A COST EFFECTIVE GRASSLAND MANAGEMENT STRATEGY TO … · n an era of acute concern about airline...

A COST EFFECTIVE GRASSLAND MANAGEMENT STRATEGY

TO REDUCE THE NUMBER OF BIRD STRIKES AT THE

BRISBANE AIRPORT

Belinda Thomson

BAppSc

School of Natural Resource Sciences

Queensland University of Technology

Brisbane, Australia

This dissertation is submitted as a requirement of the

Masters by Research Degree

2007

�

AbstrAct

�n an era of acute concern about airline safety, bird strikes are still one of the

major hazards to aviation worldwide. The severity of the problem is such

that it is mandatory in all developed countries to include bird management

as part of airport safety management programs. �n Australia, there are

approximately 500 bird aircraft strikes per year (Bailey 2000). Brisbane

airport has a relatively high occurrence of strikes, with an average of 77

recorded every year (2002-2004).

Given the severity of the problem, a variety of techniques have been

employed by airports to reduce bird strikes. Scare devices, repellents,

continuous patrols for bird hazing, use of raptors to clear airspace of birds

and depredation are used by many airports. Even given the diversity of

control methods available, it is accepted that habitat management is the

most effective long term way to control birds in and around the airport space.

Experimental studies have shown that habitat manipulation and active

scaring measures (shooting, scaring etc), can reduce bird numbers to an

acceptable level.

The current study investigated bird populations in six major vegetation

habitat types identified within the operational and surrounding areas of

Brisbane airport. �n order to determine areas where greater bird control and

management should be focused, bird abundance, distribution, and activity

were recorded and habitats that pose the greatest bird strike risk to aircraft

were identified. Secondly, species with high hazard potential were identified

and ranked according to their hazard potential to aircraft.

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This study also investigated the effectiveness of different vegetation

management options to reduce bird species abundance within operational

areas of Brisbane airport. Four different management options were

compared. Each management option was assessed for grass structural

complexity and potential food resources available to hazardous bird species.

Analysis of recorded data showed that of the habitats compared within the

Brisbane airport boundaries, grasslands surrounding runways, taxiways and

aprons possess the greatest richness and abundance of bird species that

pose the greatest potential hazard to aircraft. �bis and the Australian kestrel

were identified as the bird species that pose the greatest risk to aircraft

at Brisbane airport, and both were found in greatest numbers within the

managed grasslands surrounding operational areas at the airport.

An improved reporting process that allows correct identification of all

individual bird species involved in bird strikes will not only increase the

accuracy of risk assessments, but will also allow implementation of more

effective control strategies at Brisbane airport.

Compared with current grassland management practice, a vegetation

management option of maintaining grass height at 30-50cm reduced total

bird utilisation by 89% while utilisation of grassland by potentially hazardous

birds was also reduced by 85%.

Maintaining grass height within the 30-50cm range also resulted in a 45%

reduction in the number of manipulations required per year (11 to 6), when

compared with current management practices, and a 64% reduction in

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annual maintenance cost per hectare. When extrapolated to the entire

maintained grass area at Brisbane airport, this resulted in a saving of over

$60 000 annually.

Optimisation of potential hazard reduction will rely on future studies that

investigate the effect of particular vegetation species that could replace the

existing mix of grasses used at Brisbane airport and an understanding of the

relative importance of vegetation structure and food supply in determining

utilisation by potentially hazardous bird species.

�V

Abstract......................................................................................................... �

Table of contents ........................................................................................... . �V

List of figures................................................................................................ V��

List of tables................................................................................................. �X

List of appendices........................................................................................ X

List of Acronyms........................................................................................... X �

Statement of original authorship.................................................................. X��

Acknowledgements...................................................................................... X��

1. Projectoverview...................................................... 1

1.1 The problem ................................................................................ 1

1.2 Why Birds are Attracted to the Airport Environment..................... 3

1.3 Factors �nfluencing Birdstrikes..................................................... 5

1.3.1 Bird Size........................................................................ 5

1.3.2 Bird Abundance.............................................................. 5

1.3.3 Bird Behaviour................................................................ 6

1.3.4 Environmental Factors.................................................... 6

1.4 Techniques to Manage the Birdstrike Hazard............................... 7

1.4.1 Avoidance Techniques.................................................... 8

1.4.2 Control Techniques......................................................... 9

1.5 Experimental Site – Brisbane Airport............................................ 15

1.5.1 Current Management Practices...................................... 16

1.6 Project aims................................................................................. 16

1.7 Thesis structure............................................................................ 17

tAbleofcontents

V

2. ArisKAssessMentforoPerAtionAlAnDsUrroUnDinG

HAbitAtsAtbrisbAneAirPort...............................................18

2.1 �ntroduction.................................................................................. 18

2.2 Aims............................................................................................. 20

2.3 Methods........................................................................................ 20

2.3.1 Study area...................................................................... 20

2.3.2 Habitat description : Operational areas.......................... 21

2.3.3 Habitat description : Surrounding habitats..................... 22

2.3.4 Bird data collection......................................................... 23

2.3.5 Statistical analysis.......................................................... 26

2.4 Results......................................................................................... 27

2.4.1 Bird numbers and distribution........................................ 27

2.4.2 Bird numbers and distribution by habitat........................ 29

2.4.3 Species richness............................................................ 31

2.4.4 Monthly and seasonal bird distribution across habitats.. 33

2.4.5 Daily bird abundance..................................................... 36

2.5 Discussion.................................................................................... 38

3. AbirDHAZArDinDeXforoPerAtionAlAnDsUrroUnDinG

HAbitAtsofbrisbAneAirPort...............................................40

3.1 �ntroduction................................................................................... 40

3.2 Aims.............................................................................................. 41

3.3 Methods........................................................................................ 42

3.3.1 Study area...................................................................... 42

3.3.2 Habitat description ......................................................... 42

3.3.3 Hazard ranking data compilation.................................... 42

3.4 Results......................................................................................... 43

3.4.1 Hazardous bird presence at Brisbane airport................. 43

3.4.2 Monthly and seasonal hazardous bird abundance and

distribution.................................................................... 43

3.4.3 Daily hazardous bird abundance.................................... 46

3.4.4 Top ten hazardous bird species and distribution............ 46

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3.5 Discussion.................................................................................... 50

3.5.1 Hazardous bird presence at the Brisbane airport........... 50

3.5.2 Monthly and seasonal abundance of hazardous birds at

Brisbane airport............................................................ 52

3.5.3 Limitations on hazard ranking......................................... 53

3.5.4 Habitat hazard ranking and bird reduction

recommendations......................................................... 54

3.6.5 Other recommendations................................................. 56

4. AcosteffectiveGrAsslAnDMAnAGeMentstrAteGY

toreDUcetHenUMberofbirDstriKesAtbrisbAne

AirPort............................................................................................57

4.1 �ntroduction................................................................................... 57

4.2 Methods........................................................................................ 58

4.2.1 Study area...................................................................... 58

4.2.2 Prior to Manipulation....................................................... 58

4.2.3 Grassland Manipulation................................................. 60

4.2.4 Food Resources............................................................. 61

4.2.5 Economic analysis.......................................................... 62

4.2.6 Statistical Analysis......................................................... 62

4.3 Results......................................................................................... 63

4.3.1 Prior to grassland manipulation...................................... 63

4.3.2 Grassland manipulation................................................. 67

4.3.3 Food Resources for Birds............................................... 75

4.3.4 Economic Analysis.......................................................... 78

4.4 Discussion.................................................................................... 81

5. GenerAlDiscUssion/conclUsions.......................................86

APPenDices...............................................................................................91

references............................................................................................100

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listoffiGUres

figure2.1 Map showing (a) the location of the study site within Queensland

(b) the study site broken into habitat areas and variable circular

points in each habitat................................................................ 25

figure2.2 Average number of aircraft movement over a daily period......... 26

figure2.3 Percentage of all bird numbers observed within all habitats at the

Brisbane airport....................................................................... 29

figure2.4 Number of bird species found in habitats at the Brisbane

airport......................................................................................... 32

figure2.5 Average seasonal species richness for each habitat................. 33

figure2.6 Difference in number of birds per hectare observed in all habitats

at the Brisbane Airport................................................................ 34

figure2.7 Yearly bird abundance in each habitat at the Brisbane airport... 35

figure2.8Seasonal bird abundance in each habitat at the Brisbane

airport......................................................................................... 36

figure2.9 Difference in birds observed during three periods of the day (a)

Number of Birds per hectare (b) Number of birds/ten minutes.. 37

figure3.1 Percentage of hazardous birds observed in all habitats on and

around the Brisbane airport........................................................ 44

figure3.2 Hazardous birds observed in each habitat at the Brisbane airport

Bird numbers/hectare................................................................. 45

figure3.3 Number of hazardous birds observed over a yearly period at the

Brisbane airport: Number of birds/hectare ................................ 47

figure3.4 Average seasonal hazardous bird abundances for each habitat at

the Brisbane airport.................................................................... 48

figure3.5 Number of hazardous birds observed during the day................ 48

V��

figure3.6 Top ten hazardous bird species (based on weight) and habitats in

which they are found at the Brisbane airport.............................. 49

figure4.1 (a) Grassland management study areas within Brisbane airport

Boundaries (b) Site A (c) Site B (d) Site C............................... 59

figure4.2 Mean vegetation height (± SE) for all areas before

manipulation............................................................................. 64

figure4.3 Relative bird utilisation (birds observed/1.92ha/40min) at all sites

prior to manipulation (a) All bird species (b) Potentially hazardous

bird species................................................................................ 66

figure4.4 Mean grass height (± SE) during vegetation manipulation for

each treatment over the period June 2004-May 2005................ 67

figure4.5 Relative bird utilisation within each treatment (a) Total (b)

Monthly........................................................................................70

figure4.6 Relative bird utilisation of potentially hazardous birds within each

treatment (a) Total (b) Monthly ...................................................72

figure4.7 Relative bird utilisation (bird observed/1.92ha/40mins) during the

day (a) all bird species (b) potentially hazardous bird species....74

figure4.8 Aircraft movements at Brisbane airport.......................................75

figure4.9 Ground dwelling invertebrate abundance for each treatment type.

(Mean ± SE).............................................................................. 77

figure4.10 Foliar invertebrate abundance for each treatment type.

(Mean ± SE)........................................................................... 77

figure4.11 Dry weight of grass seeds collected from treatments

(Mean ± SE)............................................................................ 79

figureA.1 Grassland management regime for Brisbane airport................. 98

�X

listoftAbles

table2.1 Maximum number of each bird species recorded at Brisbane

Airport; % of total number of birds for each species; % of total bird

numbers for each species in each habitat................................... 28

table2.2Numbers of bird species observed in each habitat over a yearly

period........................................................................................... 32

table3.1 Bird strike data, weights and hazard ranking for bird species found

at the Brisbane Airport................................................................. 44

table4.1 Non hazardous and potentially hazardous birds observed in each

site before manipulation............................................................... 65

table4.2 Mean grass height (± SE) for each treatment over the course of

the study....................................................................................... 68

table4.3 Relative bird utilisation (birds/1.92ha/40mins) of treatment type

(mean ± SE) for hazardous, non hazardous and all bird species

over the period of the study........................................................ 69

table4.4 Utilisation of treatments by bird species..................................... 73

table4.5 Complete count of invertebrates and vertebrates (Order/Class)

sampled from pitfall traps............................................................. 76

table4.6 Dry weights of grass seed species sampled from all treatments. 79

table4.7 Mean direct costs associated with the maintenance of the various

grass height treatments................................................................80

X

listofAPPenDices

Appendix1 Species identified as present within habitats........................... 91

Appendix2 Bird stikes................................................................................ 95

Appendix3 Grassland Management Strategy............................................ 96

X�

listofAcronYMs

ATSB - Australian Transport Safety Bureau

BAC - Brisbane Airport Corporation

BAM - United States Bird Avoidance Model

G�S - Geographic �nformation System

USGAO - United States Government Accountability Office

X��

stAteMentoforiGinAlAUtHorsHiP

The work contained in this thesis has not been previously submitted for a

degree or diploma at any other educational institution. To the best of my

knowledge, this thesis contains no material previously published or written by

another person except where due reference is made.

Belinda Thomson

April 2007

X��

AcKnowleDGeMents

This study was funded by Brisbane Airport Corporation Limited (BAC) and

Queensland University of Technology (QUT) as part of an Australian first

partnership for an airport and university.

There are many people to thank:

Dr John Wilson, Peter Mather, David Elmouttie, Brendan Farthing and Peter

Prentis for their guidance, statistical prowess and manuscript editing,

John McCaffery, Karyn Rains, Phil Randall and Brett Forknall of BAC for their

organisational abilities.

The security personnel from Gate 1 at BAC for their patience and the

maintenance crew of BAC especially Clint Roberts and Geoff Barton, without

whom the study could have been accomplished.

� would also like to dedicate this paper to the memory of my supervisor Dr

John Wilson, who was and ever shall be a treasured and epochal part of the

world in which � live.

1Chapter 1. Project Overview

1. Projectoverview

1.1theproblem

Since the inception of flight in the 1900’s, men have been competing not just

with each other for air space but also with avifauna. The Wright brothers were

the first to experience problems with birds and aircraft early in the history

of flight, (Rao & Pinos 1998). The first human fatality associated with flight

in 1912 was attributed to a bird, when a gull became entangled in the flight

controls of an early model aircraft resulting in a crash (Solman 1978; Rao &

Pinos 1998; Thorpe 2003). Although bird and aircraft interactions were only a

minor concern for early aviators, this issue has become a major consideration

for modern aviation.

Around the world, instances of birdstrikes in civilian and military aviation are

estimated to approximate 30, 000 every year (ATSB 2002). Strikes incur

many costs. The most devastating of these is loss of human life. Since 1912

there have been 231 aviation fatalities linked to birdstrikes (Thorpe 2003).

The secondary cost of bird strikes includes; loss of aircraft, costly repairs and

loss of flight time due to avifaunal strikes or avifaunal interruptions to flight

schedules. The most expensive of these is loss of aircraft due to birds. Since

1990, 115 aircraft have been lost worldwide (USGAO 2001) bringing the total

of both military and civilian aircraft lost due to birdstrikes to more than 200

since the beginning of human aviation (Allen 2000). After loss of aircraft,

repair bills for damage caused by bird collisions and the loss of flight time

due to inoperative aircraft are the next major contributors to monetary cost of

bird strikes. Each year worldwide, between 1.2 and 4 billion US dollars are

spent in the aviation industry to rectify damage caused by avifauna (Short et

al. 2000; Allen & Orosz 2001). These figures are such that around the world

today most airports attempt to control wildlife hazards in and around the

aerodrome environment as part of stringent management regimes.

2 Chapter 1. Project Overview

Due to a lack of reliable reporting, total actual strikes may be much greater

than previously estimated. Reporting of birdstrikes around the world has

yet to be standardised. Every aerodrome has its own regulations, and

reporting of many birdstrikes may not even occur when there is no evidence

of damage to aircraft or pilots are unaware that aircraft have been impacted

(Van Tets 1969A; Burger 1985; Brown & Hickling 2000). In order to develop

effective management plans, reporting of all birdstrikes is essential (ATSB

2002). Previously, insufficient reliable information was collected on birdstrikes

(Blokpoel 1976) and information that was documented may have been biased

as pilots are more likely to report incidences with larger bird species than

those involving small individuals (Chilvers et al. 1997; Linnell et al. 1999).

Although birdstrikes numbers are reported each year the actual number of

birdstrikes may be up to 80% more than estimated previously. �n Australia,

an estimated 500 strikes occur per year (Bailey 2000). �n the past, reporting

of birdstrikes in Australia happened only when damage resulted to an aircraft

(ATSB 2002), which may mean the real number of strikes in the past 10

years may be up to 50% higher than statistics suggest (ATSB 2002). �n other

countries (e.g. Canada and the USA), estimates suggest that only 15 to 30

percent of all birdstrikes are reported (ATSB 2002). �n the USA alone, actual

number of birdstrikes may be up to more than 8 times that recorded in original

reports (Eschenfelder 2003).

�n spite of biases associated with reporting of birdstrikes, there is reliable

evidence to suggest that they have increased in number due to several

factors. Modern aircraft numbers are increasing and they are constructed

with quieter engines that are also capable of greater speed than in the past.

This increases the probability of birdstrikes (Solman 1981). Birds have less

time to react and avoid aircraft that approach them at faster speeds with less

noise. This may also explain why birds are involved in an increasing number

of strikes within airport environments. Aircraft takeoff requires a great burst of

speed to enable lift off and reaction times for birds are short. �n addition when


planes land, aircraft noise is reduced and this further reduces reaction time by

birds at airports (Jacobi 1996). Most bird species fly at relatively low altitudes

(except for migratory birds) and most incidences of bird and aircraft collisions

occur below 1000m (Barras & Wright 2002). Therefore possibility of strike is

greater during takeoffs and landings (Stables & New 1967; Barry 1974; Linnell

et al. 1996; Rao & Pinos 1998; Short et al. 2000; ATSB 2002). Military aircraft

flying at low altitudes (training and reconnaissance flights) and at great speeds

are particularly vulnerable (Gunn & Solman 1967; Stables & New 1967; Sodhi

2002). �n Australia from 1991-2001, 52 percent of all reported birdstrikes

within the civilian sector occurred during aircraft approach and landing, while

33 percent occurred during take off and initial aircraft assent (ATSB 2002).

�n contrast, in the military sector at least 28 percent of reported birdstrikes

occurred during flight at low altitudes (ATSB 2002). These figures are

indicative of statistics worldwide. In the absence of specific bird management

plans, incidence of birdstrikes are expected to increase due to increasing

frequency of aircraft flights (ATSB 2002).

Scientifically based management strategies to control birdstrikes are therefore

required urgently. The first step in developing such strategies will be to;

investigate major hazards on and around the aerodrome environment,

determine the risks they pose, and identify the most effective ways to reduce

risk (Allen 2000).

1.2whybirdsareAttractedtotheAirportenvironment

Most airport environs range from manicured areas for aesthetic appeal,

large areas of grassland and even agricultural crops between runways, to

surrounding urban and uninhabited areas including bushland, wetlands

and waste disposal areas. The main appeal of most airports for birds is the

availability of large areas of short grassland that is maintained continuously

between and around runways, taxiways and aprons. Birds come to these


areas to feed, drink, and rest and sometimes to nest or roost (Eschenfelder

2001; ATSB 2002). Smaller birds are believed to feel more secure when

feeding in short-grassed areas as they provide a wide field of vision for

detecting predators (Devereux et al. 2004). The fact that grass areas are

maintained continually means that insects and other invertebrates on which

birds feed are constantly disturbed which may lead to easier detection of

prey. It may also be more energy efficient for certain birds to forage for

seeds and invertebrate prey in short grass rather than having to expend

more energy searching through long grass (Butler & Gillings 2004). Birds

that feed in short grass may in turn attract larger bird predators (Eschenfelder

2001 ; ATSB 2002), which may constitute greater problems to aircraft than

will smaller birds. Large birds with large body mass pose a greater hazard to

aircraft in the event of a collision than will small birds (Dolbeer et al. 2000).

Other resources for birds are also provided by airport environments. Water

is available from drainage areas, spillways, and even standing water in lower

areas of airfields after rain. Rain may also force insects and other prey out of

the soil and onto hard surfaces such as runways, which provide easy foraging

environments for many bird species. Roosting perches or vantage points for

birds of prey are often available in the form of aircraft hangars, runway signs,

lights and vegetation such as dead trees around the perimeter of the airfield.

The airfield can also offer safety from larger predators including humans

(Wright 1967).

Around airports, natural or modified environments such as wetlands, refuse

tips, bushland and agricultural areas may also contain resources that attract

bird species (ATSB 2002). Roosting and breeding sites and food may act as

attractants for birds to these areas. Even though birds may spend most of

their time in the areas surrounding the airport, there are usually times during

the day they will cross the airspace of the aerodrome to reach resources and

thus potentially interact with aircraft. Therefore surrounding environments at


airports need to be considered along with the actual airport grounds when

considering potential avifaunal hazards and their prevention or control.

1.3factorsinfluencingbirdstrikes

Birds on airports constitute a real danger to aircraft, although not all species

may be equally hazardous. Factors including, individual size, relative

abundance and intra-specific behaviour need to be taken into account before

determining if individual species pose a threat to aircraft (Allen 2000).

1.3.1 Bird Size

As noted earlier the larger and heavier an individual is, the greater a hazard it

will present to aircraft because size and weight influence potential for damage

(Milsom 1990). Having said this, even small birds can cause serious damage.

The risk of damage to aircraft from small birds becomes greater when they

are in large numbers due to a greater chance of multiple strikes (Sodhi 2002).

1.3.2 Bird Abundance

Flocking species will have a greater chance of causing significant damage to

aircraft in the event of a collision due to potential for multiple strikes and/or

ingestion into engines (Sodhi 2002). Even though there is a greater risk of

damage with flocking species, the behaviour of large groups of birds often

enables early detection by approaching aircraft at a greater distance than will

a singular individual (Jacobi 1996).

Seasonal migratory species have high potential for striking aircraft more

often than non-migrating species, as migratory birds, especially large

bodied species, commonly fly in large groups to conserve energy (Hummel

1983; Weimerskirch et al. 2001). Migratory species are also unfamiliar with


the hazards posed by aircraft and may be relatively inefficient at detecting

approaching aircraft (Sodhi 2002). Migrating species are also more likely to

be involved with strikes due to fatigue (Sodhi 2002) as some migrate tens

of thousands of kilometres. Bird species that are residents at airfields can

develop avoidance behaviour and hence may not pose as significant a threat

of collision as seasonal migrating species. Thus relative abundance, size and

familiarity with the airfield environment can contribute to bird strike probability.

1.3.3 Bird Behaviour

Behaviour of certain bird species may increase their birdstrike potential.

Juveniles may pose significantly higher risks than adults as a result of a lack

of learned behaviour from parents to avoid aircraft (Jacobi 1996), or they

may be less able to avoid aircraft once a danger is perceived because of

inexperience in manoeuvrability and/or lack of strength (Solman 1981; Sodhi

2002).

Some birds are opportunistic feeders and can take advantage of potential

food resources that are disturbed when maintenance is carried out on

grasslands surrounding runways. As a result, birds feeding on these

resources can be brought into closer proximity with aircraft, which may

increase the risk of a birdstrike.

1.3.4 Environmental Factors

Although some birds are active during all hours of the day and during the

night most activity usually occurs in the first hours after sunrise (Robbins

1981). Higher activity rates at this time, means that strikes are more likely to

occur during these times, although this is not always the case, as birdstrikes

have been reported over the complete 24 hour period (Blokpoel 1976).

Most however, occur during the day, a small proportion happen at night,


but only a relatively small proportion of strikes happen in the early morning

periods (Neubauer 1990). The length of daylight hours may also affect risk of

birdstrike. Most bird/aircraft collisions occur in late summer and early autumn

(Kelly et al. 2003) when hours of daylight are longer, compared with numbers

of strikes in late autumn and early winter.

Along with daylight length, intensity of light can also have an impact on bird

behaviour and an individual’s ability to avoid collisions with aircraft. Research

is underway to determine the effect that ambient light conditions may play on

birdstrike potential (Fennessy et al. 2003).

Weather conditions can also affect bird behaviour. �nclement weather may

alter some bird species foraging behaviour and this lull in activity also reduces

potential for birdstrike during these times (Neubauer 1990; Manktelow 2000).

1.4techniquestoManagethebirdstrikeHazard

Birdstrike reduction is a major issue for airports and aerodromes around the

world and as each airfield has its own set of circumstances, management

of bird presence varies. �n order to manage bird populations or reduce

birdstrikes effectively there are many options that can be applied at most

airports, each with differing rates of success. They can be separated into two

broad categories:

• Avoidance Techniques

• Control Techniques

a. Dispersal

b. Habitat Management


1.4.1 Avoidance Techniques

Due to the fact that the airport environment is attractive to many bird species

(Wright 1967), it is often very difficult to stop all birds from entering. To

address this, systems have been developed to act as a warning to both airport

and aircraft personnel of potential bird hazards. There are different ways

to determine bird presence around the airport vicinity, including detection

technology such as radar that can pick up presence of birds in large numbers,

or routine reports by airport security patrols.

Use of radar for bird hazard advisory systems began in the 1960’s when

radar systems regularly detected echoes that at first could not be identified

(Schaefer 1967). A vast majority of these echoes, termed “point angels”,

were later found to be birds (Schaefer 1967). Since the first detection of

birds by radar, radar ornithology has progressed significantly. Radar is now

used to track migrating birds and to warn airports within bird flight paths, so

that avoidance strategies and birdstrike warnings can be activated (Leshem

& Froneman 2003; Ruhe 2003). Unfortunately birdstrike warnings from radar

usually happen only after avian groups are detected.

The United States Air Force Bird Avoidance Model (BAM) is used to predict

when groups of migrating birds will arrive. �t was developed in the early

1980’s and uses historical population data on waterfowl and raptors to predict

birdstrike risk for low level aircraft training routes (Lovell & Dolbeer 1999).

Early versions of BAM were limited in their use, but with the introduction

of Geographic �nformation Systems (G�S), BAM now is able to display a

birdstrike risk for areas of 1km over the entire US land mass (DeFusco 2000).

This ability to predict where and when bird hazards are likely to occur in the

United States has saved millions of dollars for military aviation. There is a

great need to apply this technology more widely.


A pilot’s knowledge of conditions around airports and likely presence of

birds can do much to minimise and avoid birdstrikes (Eschenfelder 2001).

Warnings from the airfield tower about presence of birds in the area help

to reduce risk of birdstrikes as can information from personnel around the

runways and taxiways.

Employing warnings that result in pilots avoiding hazards can reduce the

number of birdstrikes, yet it does not decrease the hazard itself. Fewer birds

present on airfields will result in fewer birdstrikes. Different techniques can be

employed to control the number of birds present in airport habitats and these

will be discussed next.

1.4.2 Control Techniques

There are many tactics employed by airports around the world to try to

reduce the number of birds that occur within aerodrome domains. These

can be divided into two distinct approaches: dispersing and dissuading

birds from remaining after they have arrived or initially deterring their arrival

by manipulating the local environment so that birds do not find aerodrome

habitats favourable.

1.4.2.1 Dispersal Techniques

Removal of bird species from areas where aircraft operate has been a

management strategy that has been trialed at almost every airfield that

has experienced bird hazards. Many techniques have been applied with

varying degrees of success. The most widely used today include: shooting;

frightening devices, involving pyrotechnics and electronic devices like bird

distress calls; and use of predatory stimuli.


Shooting or culling birds, can reduce the physical number of birds present and

hence can reduce birdstrike probability (Dolbeer et al. 1993). This practice is

often not favoured and depredation is a last resort. �t is only carried out after

special permits are obtained from local authorities. Some bird species have

even been shown to alter their flight path to avoid aerodromes that employ

shooting as part of their bird management strategy (Dolbeer et al. 2003). The

problem can be however, that territory that was formerly occupied is now

open for other bird species to invade (Van Tets 1969 A). This can raise an

additional problem, as birds filling vacant niches may be less experienced with

aircraft avoidance and therefore risk of strike may increase (Burger 1983).

Pyrotechnics and the use of bio-acoustics or amplified bird distress calls have

also been shown to be successful for removing birds from airfields (Busnel

& Giban 1967; Baxter 2000; Ryjov 2000). Pyrotechnics employ the use of

visual and audio aids to scare birds away from areas if a threat is perceived.

Devices such as shell crackers which are fired from a shotgun and explode

loudly, force many bird species into flight but if they are used in isolation, birds

eventually habituate to the noise reducing their effectiveness (Blokpoel 1976;

Baxter 2000).

Another technique employed to deter birds from airports is the use of taped

distress calls that target specific bird species. Tapes of warning calls or

distress calls of specific species of bird are replayed over loud speakers in

areas where the species aggregate. This techniqe has been shown to work

with certain species of bird on airfields (Busnel & Giban 1967), but with some

flocking birds initial flight is followed by an investigation of the source of the

calls which usually results in only slow departure from the airfield space

(Busnel & Giban 1967). Depending on bird species, use of distress calls may

actually attract birds to the calls first instead of scaring them away (Airforce

1997). This can increase strike risk and application of this technique needs to

be timed so as to ensure that dispersal occurs before the next aircraft arrival


or departure (Brough 1967). Limitations of dispersal techniques include

that; they can take an extended period of time to work, and the use of bio-

acoustics is also an expensive alternative that requires high maintenance.

The approach has been efficient at some airports while completely ineffective

at others (Ryjov 2000) even when used in conjunction with other control

methods. This is because birds tend to habituate to the calls (Baxter 2000).

Another control method that has proven to be successful when used in

conjunction with distress calls, are use of predatory species. Using an animal

or bird species that hazardous species would usually be wary of such as birds

of prey or dogs have proven effective. Distress calls are sometimes used

that usually attracts target species and then predatory species are released

resulting in hazardous species leaving the aerodromes in large numbers

(Tomsons 1998). Falconry programmes are in place at some airports around

the world and can greatly reduce the number of birdstrikes (Tomsons 1998).

Although falcons can be an extremely effective control method, they have

many disadvantages. Both birds and handlers need extensive training, birds

cannot be used during inclement weather and they cannot be flown at night

(Brough 1967).

Some airports have employed dogs to disperse birds from airport habitats,

with great success, resulting in a reduction of 29 to 40 percent in hazardous

species and up to a 50 percent reduction in bird numbers (Patterson 2000;

Carter 2003; Froneman & Van Rooyen 2003). Reduction of bird numbers,

in turn, will reduce the number of birdstrikes, and the use of dogs has at

some airports reduced the instances of bird strike to zero (Patterson 2000;

Carter 2003; Froneman & Van Rooyen 2003). Although employing predators

has been successful there are high associated costs that may render this

technique a major problem at many airports.


All of the techniques used currently to actively scare or remove birds from

airfields may be useful when used in conjunction with other applications.

Most work for only a short period of time however, before habituation and

other factors make them inefficient. An alternative strategy used at a

number of airports around the world to reduce numbers of birds is that of

long term manipulation of the airport environment to make it less appealing

to hazardous bird species (Mead & Carter 1973; Brough & Bridgman 1980;

Buckley & McCarthy 1994; Crossfield 2001). This approach will differ for

individual airfields taking into consideration differences in surrounding habitat,

what hazardous avifaunal species are present and financial constraints.

1.4.2.2 Habitat Management Techniques

�n order to remove or reduce hazardous birds from airports, factors that

attract birds need to be reduced or removed. A large proportion of airports

around the world maintain grassland between and around the operational

areas (runways, taxiways and aprons). Maintenance of grassy areas to a

specific height has been shown to reduce numbers of certain bird species that

may be a hazard to aircraft (Mead & Carter 1973; Brough & Bridgman 1980;

Buckley & McCarthy 1994; Crossfield 2001). Many bird species are attracted

to short grass (5-10cm) for feeding, resting and safety reasons. Areas of

short grass can offer birds a large area of easily accessible food in the form

of invertebrates that thrive in the fertile soils of continuously mown areas.

Associated with ease of food access is the safety associated with short grass

as birds can gain good ‘line of sight’ for detecting predators (CAA 2002;

Devereux et al. 2004).

The “long grass policy” (Mead & Carter 1973), that has been adopted at

some airports, maintains the length of grass at 15-20cm or higher to dissuade

use by birds (Brough & Bridgman 1980; Buckley & McCarthy 1994). This

policy is based on the premise that long grass deters birds from foraging for


invertebrates and that it also reduces bird acuity thus making these areas

less secure to rest and feed (Dekker 1996). However, the approach does

have some disadvantages. Maintaining long grass on airfields may actually

increase soil fertility in turn increasing invertebrate numbers. Numbers of

prey for birds can thus actually increase (Dekker 1996). This results from

the requirements for maintaining long grass. Each spring the long grass is

cut down and removed. The area is then fertilised to ensure rapid and lush

growth of new grass. Maintenance for the rest of the year involves cropping

the grass when it gets to a specified length (Deacon & Rochard 2000)

but usually the cropped grass is left and decomposes providing additional

fertilisation for the grassed areas until it is removed again during the spring

cutting. Long grass may also become a preferred habitat for nesting birds

and birds that forage in longer grasses (Seamans & Dolbeer 1999) which

may add to aircraft hazards. Rodents and other small vertebrates may also

find long grass satisfies their specific needs, in turn attracting larger birds of

prey which prove to be a greater hazard to aircraft due to their flight behaviour

when searching for prey.

Another approach to make airfield grounds less appealing to unwanted

avifauna species requires maintaining a poor long grass regime. This

application, while still maintaining a specific length of grass, focuses on

reducing soil fertility (Dekker 1996, 2000). This is accomplished by not

fertilising the grass each cycle and removing clippings after the grass has

been cut to the required length. Regular removal of grass clippings is

however a costly method in view of the time and man power required and

the need to remove clippings to areas that will not be disturbed by aircraft

(BAC pers comm). This can require transport to areas outside the airport

environment which requires extra time, effort and cost. Reduction of biomass

may also render areas surrounding the runways subject to erosion from

engine thrust. This can jeopardise aircraft safety.


An alternative habitat manipulation approach involves replacing grass

with alternative plants that are less appealing to hazardous bird species

(Blockpoel 1976, 2003). The choice of the replacement vegetation must

suit requirements of being unattractive to both birds and invertebrates as

both a food source and an area of cover (Austin-Smith & Lewis 1970). This

needs to be adapted independantly for each airfield taking into consideration

the species of birds determined to be most hazardous. Replacement of

vegetation can be extremely costly however, but the long term benefits may

outweigh initial outlays (Wright 1967).

Other procedures for bird control that have been trialed include: changing

colour of landing lights to reduce insect attraction and therefore indirectly

reducing the number of birds that prey on this source of food (Van Tets et

al. 1969 B); spraying chemicals to poison or disperse birds (Blokpoel 1976;

Engeman et al. 2002); use of insecticides to reduce the abundance of food

resources for birds (Engeman et al. 2002); adapting infrastructure on the

airfield to reduce bird structural attractants (Tomlin et al. 1981; Dekker 2003);

manipulating habitats surrounding airports that may be roosting areas for

birds considered hazardous to aircraft (Weitz 2003); or manipulating attractive

areas outside the airfield such as land fill sites that may cause birds to fly over

the airfield in order to reach the resource (Cleary & Dolbeer 1999).

Although there are a variety of bird hazard management approaches, none

are considered as ‘standard’ at all airportss or aerodromes. While habitat

management is generally considered to offer the best reduction in numbers of

birds over a period of time, birds can still be found in unattractive habitats from

time to time (Wright 1967). Dispersal and habitat management approaches

used in combination are likely to provide the best solution for decreasing the

bird numbers at airports. Specific approaches must however, be adapted to

each new situation.


1.5experimentalsite–brisbaneAirport

The Brisbane airport is located 13 km north east of the centre of Brisbane

and covers 2700 hectares of land. Original vegetation has been cleared

extensively and now only seven main vegetation communities are found

within the airport boundaries. �n the past, Brisbane airport has not had a great

problem with avifauna associated with these habitats, and the birdstrike rate

was relatively low. From 1966 till 1973, there were a total of 140 birdstrikes

recorded and most resulted in no damage (Barry 1974). Today however,

Brisbane airport has one of the highest strike rates of any Australian airport

each year. The number of strikes averaged 33.2 per year from 1996-2000

(Pell & Jones 2002), and since then there were 71 reported in 2002 (Rhodes

& Jones 2004), 79 reported in 2003 (pers comm. BAC 2004) and 81 reported

in 2004 (pers comm. BAC 2005). Thus the need to develop more effective

bird hazard management plans for the Brisbane airport has been recognised

as a priority for airport management.

1.5.1 Current Management Practices

Brisbane airport has already instigated some management plans to deal with

potential bird hazards. A large tree plantation, regarded as poor fauna habitat

(BAC 1999), was established with a monoculture of Casuarina glauca in order

to render surrounding habitats at the airport, unattractive to birds. �n addition,

a local refuse tip that was originally near the airport was found to be attracting

large numbers of Silver Gulls (Larus novaehollandiae), which were also using

the airfield grounds as a resting area. The refuse tip was relocated and the

number of gulls recorded at the airport subsequently, was reduced to zero.

Removal of shallow-water feeding areas and bird attracting wetlands has also

been incorporated in the management plan for avifaunal species found at

the Brisbane airport (BAC 1999). The Brisbane airport also employs a bird

dispersal technique, cracker shot (exploding cartridges fired from a shot gun),


that helps to dissuade birds from using the airport grounds. Although these

management plans are in place, instances of birdstrikes still remain high.

1.6Projectaims

�n order to reduce bird strike risk, more action needs to be taken.

Identification of areas that can be considered as a hazard to aircraft and an

extensive risk assessment are required. The Brisbane airport lacks a defined

scientific habitat management option for the vast grasslands surrounding

runways, taxiway and aprons to encourage birds to go elsewhere. Any

habitat management scheme should be aimed at deterring use by the most

hazardous bird species present at the Brisbane airport.

Accordingly this study aims to:

(1) Determine habitats within the Brisbane airport boundary that are most

hazardous to aircraft in relation to bird abundance and activity so that

management can be directed specifically at these areas (Chapter 2);

(2) Assess historical bird strike data at Brisbane Airport to determine

which bird species are hazardous to aircraft and combine this

knowledge with findings from Chapter 1 to identify areas that are

considered to offer the greatest potential for bird strikes. Once these

areas have been determined, effort can be directed at reducing bird

strike potential according to a weighted scale from greatest to least

hazard potential (Chapter 3);

(3) Determine a vegetation management strategy for the habitat(s)

determined to be most hazardous with regard to bird utilisation.

Vegetation management will need to be cost effective and efficient

at reducing number of potentially hazardous bird species within the

airport environment (Chapter 4).


Results from the experiments conducted here will provide the Environmental

Management Team at the Brisbane airport with options for better habitat

management techniques that will decrease the number and species of

birds found at the Brisbane airport and therefore in turn reduce the risk and

instance of birdstrike.

1.7thesisstructure

Each chapter within this thesis covers specific issues that builds on the

results of the previous chapter. Thus, the thesis presents a logical sequence

of the ideas necessary to develop a scientific management strategy to

reduce number of bird strikes at the Brisbane airport. Each chapter provides

sufficient background information so that they may be read and understood

seperately (and due to this the methods section of chapter 2 and 3 - Study

area and habitat description are repeated). The thesis concludes with a

general discussion of the results of each study and their implications for

management now and research directions identified for the future.

18 Chapter 2. A risk assessment of Brisbane Airport habitats

2. ArisKAssessMentforoPerAtionAlAnDsUrroUnDinGHAbitAtsAtbrisbAneAirPort

2.1introduction

Bird strikes are a major hazard to aircraft. Annually, civilian and military

aircraft are involved in over 30 000 birdstrikes around the globe (ATSB

2002). Bird strikes have resulted in a significant loss of human life with 231

human related fatalities since 1912 (USGAO 2001). The accumulated cost

of bird strikes has been estimated at between 1.2 and 4 billion US dollars

in repairs and other associated costs (Short et al. 2000; Allen 2002). As a

consequence, most aerodromes around the world incorporate a management

regime that focuses on reducing bird presence within and around the airport

environment.

Birds are attracted to airport environments for many reasons. Most

aerodromes have large grassland and vegetated areas and these habitats

offer significant opportunities for foraging, nesting and many other habitat

related requirements (eg. water for drinking and areas for roosting) (ATSB

2002). The main appeal of many airports for birds are large areas of short

grass that are maintained continually between and around runways, taxiways

and apron areas. Birds come to these areas to feed, drink, and rest and

sometimes to nest or roost (Eschenfelder 2001; ATSB 2002). Some smaller

species may select short-grassed areas when feeding as these areas may

provide them with a wider field of view to detect predators (Mead & Carter

1973). The fact that grassy areas are maintained continually means that

insects and other invertebrates that birds feed on are constantly disturbed and

easily visible, which may allow birds to expend less energy when foraging for

prey.

19Chapter 2. A risk assessment of Brisbane Airport habitats

Most management options employed at airports for controlling birds are

costly and time consuming and are often designed to scare birds away from

the airport environs. Scare options are usually rendered inefficient after

prolonged use as many bird species can habituate to the noxious stimuli

employed (eg. visual and auditory scaring techniques) (Blokpoel 1976; Baxter

2000; Ryjov 2000). Another effective method for managing bird presence

has been to manipulate favoured habitats within the airport and surrounding

areas (Solman 1969, Burger 1983, Buckley & McCarthy 1994). With proper

management, airfields and their surrounds can be converted into areas that

birds find less attractive and hence numbers can be reduced. Combining

habitat manipulation with strategic bird scaring techniques is generally

considered to be the best approach for controlling bird populations at airports

(Solman 1969; Burger 1983; Rao & Pinos 1998; Bailey 2000).

Australian airports are familiar with the hazards of bird strikes. The Brisbane

Airport is one of Australia’s major airfields and regularly reports a high number

of aircraft/wildlife strikes (ATSB pers comm.) with 79 strikes reported in 2003

(67 of them involved birds). Although Brisbane airport employs scare tactics

(use of cracker shot - exploding cartridges fired from a shot gun) as the main

bird deterrent, the number of bird strikes has increased over previous years.

This clearly demonstrates a need to develop improved management options.

Management options must reduce the number of birds present on and around

the airfield and also be cost effective.

Brisbane Airport is an area that contains many different habitats both within

the operational zones and the surrounding areas that have potential for

attracting bird species that are hazards for aircraft. As a starting point for

developing better management regimes for birds at Brisbane Airport, a study

of bird diversity and density in airport operational areas and surrounding

habitats is required to determine the habitats that contain the greatest

abundance of bird life and therefore that could attract birds that may pose


a risk to aircraft. Major habitat types and their distribution and abundance

at Brisbane airport need to be defined and a risk assessment for each area

needs to be carried out, in relation to the bird species that are present there.

2.2Aims

The objectives of the bird risk assessment were to:

(1) Assess avifaunal population parameters including species present,

relative abundance, habitat areas utilised and peak activity periods

(seasonally, monthly and daily).

(2) �dentify habitat types at Brisbane airport that contain the greatest

abundance of bird species.

2.3Methods

2.3.1 Study area

Brisbane Airport is Australia’s third busiest international airport and operates

two major runways. The airport is located 13km Northeast of Brisbane

(153o06’59”E; 27o23’09”S) and occupies an area of 2700 hectares. The

Airport lies on a reclaimed floodplain close to the mouth of the Brisbane River

and is bounded by Moreton Bay Marine Park to the North, Jackson Creek

marine habitat and mangroves to the North West, Boondall Wetlands to the

West and Boggy Creek and Bulwer �sland to the East. The 2700 hectares

covered by the airport contains seven different major habitat types both within

the operational and surrounding areas of the airport (ERM 2002). Of the

seven different habitat types, two are present in operational areas (directly

influenced by the movement of aircraft) and all others occur in surrounding

areas.


2.3.2 Habitat description : Operational areas

2.3.2.1 Managed grasslands

Managed grasslands surround the runways, taxiways and aprons of both the

international and domestic terminals. These areas contain a diverse array of

species of grass, sedges and broad leaf plants and are subject to invasion of

many weed species, especially in areas that are not maintained frequently by

mowing. Common species found within the managed grassland areas include

Couch (Cynodon dactylon), Rhodes Grass (Chloris gayana), Kikuyu Grass

(Pennisetum clandestinum), Spring Grass (Eriochloa procera), and Paspalum

(Paspalum dilatum) (ERM 2002). The large grassland areas provide ideal

habitat for many bird species in the form of grass seed, insects and standing

water after rainfall.

2.3.2.2 Unmanaged grasslands

Unmanaged grasslands are located adjacent to, and at either end, of the main

runway. Species composition include dense wetland communities of mostly

reeds (eg Common reed - Phragmites australis) and sedges (eg Bunchy

Sedge - Cyperus polystacyous), but also some varieties of grass and weed

species that have been left to grow to full size including Rhodes Grass and

Groundsel Bush (Baccharis halimifolia) (ERM 2002). These areas provide

shelter for some reptiles, and mammals which may in turn attract species of

birds such as raptors that prey on them. Unmanaged grassland also provide

requirements for some grass dwelling and wading bird species.


2.3.3 Habitat description : Surrounding habitats

2.3.3.1 Casuarina plantations

Very large plantations of Swamp oak (Casuarina glauca) were established

around operational areas at Brisbane Airport, as casuarinas are known to

be a habitat not favoured by most avifauna (BAC 1999). �n the years since

planting, undergrowth species such as Lantana (Lantana camera), Wild

Tobacco (Solanum mauritianum) and other weed species have become

established in the plantations, providing additional habitat for some bird and

mammal species (ERM 2002). Within the Casuarina plantation are small

remnants of emergent vegetation such as eucalypts (Eucalyptus spp) which

may also provide nesting opportunities for some bird species.

2.3.3.2 Canal, freshwater wetland and sedge communities

These areas are similar in plant species composition to the operational

unmanaged grasslands but also contain emergent vegetation including

casuarina (Casuarina spp), and eucalypt species that supply some larger bird

species with roosting, nesting and observation points.

2.3.3.3 Mangrove forests

Mangrove communities at Brisbane airport include both remnant areas

surrounding the larger creeks (Jackson Creek, Serpentine Creek and

Serpentine Creek �nlet) around the airport, and new colonies that have

established in the canals constructed within the airport’s operational

boundaries (Airside) and in canals outside the operational boundaries (eg

Schulz Canal, Landers Pocket Drains). Species include Grey Mangrove

(Avicennia marina), River Mangrove (Aegiceras corniculatum), Yellow

Mangrove (Ceripos tagal var australis) and the Red Mangrove (Rhizophora


stylosa) (ERM 2002). Tidal mudflats and salt marsh communities are also

present within some mangrove areas. These areas provide aquatic bird

species and migratory waders with an ideal substrate for foraging and also

roosting areas that are not easily accessible to many predators.

2.3.3.4 Coastal dunes and foreshore

Foreshore habitat at Brisbane Airport is made up of mudflats and sandy flats

at low tide. The dunes system is small and confined to the northern end of

the airport and the Serpentine �nlet. �t contains some species of casuarina, a

long strip of maintained grassland and patches of unmanaged grassland. The

Serpentine inlet is tidal but retains a large amount of water in a lake setting at

low tide. The large area of mudflats provides excellent grounds for migratory

waders to feed, as well as many areas for roosting. The Serpentine �nlet also

provides areas for aquatic bird species such as ducks and herons to rest and

forage.

2.3.3.5 Landscaped areas

These areas are maintained grassland with planted native and exotic species

that run the length of airport drive. As no manipulation is contemplated to

reduce the presence of bird species in these areas, they were not considered

further here.

2.3.4 Bird data collection

Maps of the Brisbane airport showing each habitat type were divided into

250m X 250m grids to allow reference points to be located at least 250m

apart in closed habitats and 500m apart in open habitats (Ralph et al. 1993).

Within each habitat three points were chosen at random giving a total of 18

points (Figure 2.1). Only a single observer was used to reduce observer


bias, so more points were not established. These points became the centre

for a variable circular point count (Reynolds et al. 1980 DeSante 1986),

conducted monthly for twelve months. Each point on the non operational area

was marked with a stake and then circles radiating 10m were marked in the

cardinal directions with flagging tape, for 40m. Within the operational area, no

markers were placed as these were potential FOD (Foreign Object Damage)

for aircraft. �nstead estimations of 0-10m, 10-20m, 20-30m, 30-40m and

<40m, were used.

The bird census took place every month (July 2003 – June 2004), over a

period of three days. Each day was divided into three census periods; three

hours after sunrise, three hours over the midday period, and three hours

before sunset. Times were chosen to represent periods of greatest activity for

bird species (Robbins 1981) and also during the major operational times for

aircraft at the Brisbane airport (peak aircraft movement morning, midday and

late afternoon/early evening) (Figure 2.2).

Two habitats were visited each day, with each of the three points within

each habitat visited in each of the three time periods. Order of visitation

was randomised prior to commencement of observations. Half an hour was

allowed at each point, to enable travel between census points within the three

hour allotted time period. A period of ten minutes was spent at each point

(Reynolds et al. 1980; Fuller & Langslow 1984), after a settling period of one

minute (Reynolds et al. 1980; DeSante 1986; Rosenstock et al. 2002), and

all birds within the designated areas were identified to species using both

sightings and bird call. The data were recorded for each radiating circle, and

separated into three time periods, 0-3mins, 3-6 mins and 6-10mins.


figure2.1 Map showing (a) the location of the study site within Queensland;

(b) the study site broken into habitat areas and Variable Circular Points in each

habitat.


figure2.2 Average number of aircraft movement over a daily period.

Birds that utilised the census area for food, foraging, hunting, resting and

nesting were recorded. Any birds that flew over the area (excluding birds

hunting) were not included as using the area for resources. To reduce bias

and to increase the precision of bird counts the same observer was used for

all bird counts (Cunningham et al. 1999). Bird observations were restricted to

days when weather conditions did not interfere with the detections of birds, eg

rain, excess wind and fog (Ralph et al. 1993).

2.3.5 Statistical analysis

All data were entered into SPSS 11.5 for windows, and tested for normality.

Transformations of log +1 were applied where necessary. 2 way ANOVAs

(analysis of variance) were conducted on all data to determine the signifi-

cance of bird population parameters.

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2.4results

2.4.1birdnumbersanddistribution

A total of 101 bird species were observed within the Brisbane airport

boundaries (Appendix 1). The Straw necked ibis (Threskiornis spinicollis)

was the most abundant species contributing 15.06% of all birds recorded.

The second most abundant species was the Fairy martin (Hirundo ariel)

comprising 8.07% of the total (Table 2.1)

Many species were found only in specific habitats, for example: Richard’s

pipit (Anthus novaeseelandiae) was only observed in the managed

grasslands; Mangrove gerygone (Gerygone levigaster) was only observed in

mangrove forests; Rufous whistler (Pachycephala rufiventris) was found only

in casuarina plantations; Lewin’s rail (Rallus pectoralis) was found only in

canal wetland communities; while other species such as the Australian white

�bis or Sacred ibis (Threskiornis aethiopica), Straw necked ibis and Australian

kestrel (Falco cenchroides) were identified in more than a single habitat

(see Appendix 1). The Torresian crow (Corvus orru) was observed in all six

habitats.

Of all bird numbers observed, 40% were recorded in the managed grassland,

18% were observed along the coastal dunes and foreshore, 15% were

observed within the unmanaged grasslands, 13% within the casuarina

plantations, 11% within the canal wetland communities, and the lowest

percentage of bird species, 3%, was found in the mangrove forests (Figure

2.3).


table2.1 Maximum number of each bird species recorded at Brisbane

Airport; % of total number of birds for each species; % of total bird numbers

for each species in each habitat.

% bird Abundance (top 15) In each habitat

Bird Species

Max

count

% of Total Count

1 2

3 4

5 6

Straw necked Ibis (Threskiornis spinicollis ) Fairy martin (Hirundo ariel) Golden headed cisticola (Cisticola exilis) Silver gull (Larus novaehollandiae) Tawny grassbird (Megalurus timoriensis) Red necked stint (Calidris ruficollis) Sacred Ibis-(Threskiornis aethiopica) Torresian crow (Corvus orru) Red knot (Calidris canutus) Richard’s pipit (Anthus novaeseelandiae) Sharp tailed sandpiper (Calidris acuminata) Pacific black duck (Anas superciliosa) Curlew sandpiper (Calidris ferruginea) Whimbrel (Numenius phaeopus) Magpie-lark (Grallina cyanoleuca) Gull billed tern (Sterna nilotica) Welcome swallow (Hirundo neoxena) Bar tailed godwit (Limosa lapponica) Rufous whistler (Pachycephala rufiventris) Chestnut teal (Anas castanea) Common starling (Sturnus vulgaris) Varied (mangrove) honeyeater (Lichenostomus versicolor) Cattle egret (Ardea ibis) Grey fantail (Rhipidura fuliginosa) Australian magpie (Gymnorhina tibicen) Chestnut breasted mannikin (Lonchura castaneothorax) Masked lapwing (Vanellus miles) Black winged stilt (Himantopus himantopus) Mangrove gerygone (Gerygone levigaster) Eastern Curlew (Numenius madagascariensis) Red-capped plover (Charadrius ruficapillus) Pied oystercatcher (Heamatopus longirostris) Sanderling (Calidris alba) Grey shrike thrush (Colluricincla harmonica) Australian kestrel (Falco cenchroides) Red-backed fairy wren (Malurus melanocephalus) Brown quail (Coturnix pectoralis) Grey butcherbird (Cracticus torquatus) Mongolian (lesser) sand plover (Charadrius mongolus) Olive backed oriole (Oriolus sagittatus) Silver eye (Zosterops lateralis) Black shouldered kite (Elanus notatus)

Collared kingfisher (Halcyon chloris) Grey tailed tattler (Tringa brevipes) Royal spoonbill (Platalea regia) Little grassbird (Megalurus gramineus) Tree martin (Hirundo nigricans) Common Sandpiper (Actitis hypoleucos) Australian pelican (Pelecanus conspicilatus) Crested pigeon (Ocyphaps lophotes) Intermediate egret (Egretta intermedia) Black faced cuckoo shrike (Coracina novaehollandiae) Black tailed godwit (Limosa limosa) White faced heron (Ardea novaehollandiae) Pied cormorant (Phalacrocorax fuscescens) Whistling kite (Haliastur sphenurus) Terek sandpiper (Tringa terek) Little black cormorant (Phalacrocorax carbo) Willy wagtail (Rhipidura leucophyrs) Lesser golden plover (Pluvialis dominica) Little egret (Egretta garzetta) Brahminy kite (Haliastur indus) Caspian tern (Hydropogne caspia) Forest kingfisher (Halcyon macleayii) Pied Butcherbird (Cracticus nigrogularis) Common greenshank (Tringa nebularia) Little Curlew (Numenius minutes) Little pied cormorant (Phalacrocorax varius) Spangled drongo (Dicrurus bracteatus) Pale headed rosella (Platycercus adscitus) Leaden flycatcher (Myiagra rubecula) Swamp harrier (Circus approximans) White-breasted sea eagle (Haliaeetus leucogaster ) Brown Honeyeater (Lichmera indistincta) Great egret (Egretta alba) Brown gerygone (Gerygone mouki) Mangrove (striated) Heron (Butorides striatus) Lewin's rail (Rallus pectoralis) Brown falcon (Falco berigora) Galah (Cacatua roseicapilla) Rainbow lorikeet (Tricholglossus haematodus) Marsh Sandpiper (Tringa stagnatilis) Striped Honeyeater (Plectorhyncha lanceolata) Noisy Miner (Manorina melanocephala) Osprey (Pandion haliaetus) Greater (large) sand plover (Charadrius leschenaultii) Brown Goshawk (Accipiter fasciatus) Dollar Bird (Eurystomus orientalis) Mistletoe bird (Dicaeum hirundinaceum) Spotted Harrier (Circus assimilis) Rainbow bee-eater (Merops ornatus) Black bittern (Ixobrychus flavicollis) Australian darter (Anhinga melangaster) White eared honeyeater (Lichenostomus leucotis) Yellow faced honeyeater (Lichenostomus chrysops) Clamorous reed warbler (Acrocephalus stentoreus)

788 422 361 324 292 282 270 215 208 147

99 98 96 92 91 87 78 77 76 75 74 72 63 63 63 62 50 45 43 36 34 33 32 32 29 28 25 24 23 23 22 22

22 21 21 19 16 15 15 15 14 14 13 13 12 11 11 11 11 10 10

8 8 8 8 7 6 6 6 6 5 5 5 4 4 4 3 3 3 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 1

14.33%

7.68% 6.57% 5.89% 5.31% 5.13% 4.91% 3.91% 3.78% 2.67% 1.80% 1.78% 1.74% 1.67% 1.66% 1.58% 1.41% 1.40% 1.38% 1.43% 1.42% 1.36% 1.15% 1.15% 1.15% 1.13% 0.91% 0.82% 0.78% 0.69% 0.65% 0.63% 0.61% 0.61% 0.55% 0.49% 0.45% 0.46% 0.44% 0.44% 0.42% 0.42%

0.42% 0.40% 0.40% 0.36% 0.29% 0.29% 0.29% 0.29% 0.27% 0.27% 0.25% 0.25% 0.23% 0.21% 0.21% 0.21% 0.21% 0.19% 0.19% 0.15% 0.15% 0.15% 0.15% 0.13% 0.11% 0.11% 0.11% 0.11% 0.10% 0.10% 0.10% 0.08% 0.08% 0.08% 0.06% 0.06% 0.06% 0.04% 0.04% 0.04% 0.04% 0.04% 0.04% 0.02% 0.02% 0.02% 0.02% 0.02% 0.02% 0.02% 0.02% 0.02% 0.02% 0.02%

38.34 14.21 2.86

0.89

10.23 3.93

5.99

1.79

4.02

2.06

2.77

2.73

2.64

1.70

1.07

6.52 30.27

20.07

12.88

2.84 2.34 0.84

5.69

3.51

4.52

2.51 2.01

1.34

1.17

0.50

12.94

28.63

22.35

1.96

0.78

10.20

9.02 3.53

0.78

1.57

0.78

0.78 1.57

0.78

0.78

1.06 30.24

39.79

3.45

4.77

2.92 3.18

3.71 1.06

1.86

1.06

1.06

1.06 0.80 1.06

1.85

7.41 3.70

0.93 0.46

31.94

2.31

19.44

12.04

9.26

0.46

4.63

3.70

0.93

0.46

3.58

17.45

14.31

11.27

3.36 2.76 5.53 5.04

4.72

4.12

3.36

2.44

2.01 1.84 1.84

Double banded plover (Charadrius mongolus) 22 0.42%

Bar shoulderd dove (Charadrius bicinctus) 1 0.02%Fuscous honeyeater (Lichenostomus fuscus) 1 0.02%Lewin’s honeyeater (Meliphaga lewinii) 1 0.02%Kookaburra 1 0.02%(Dacelo novaeguineae)


Note (for table 2.1):

1. Managed grassland 2. Unmanaged Grassland

3. Casuarina Plantation 4. Canal Wetland Communities

5. Mangrove Forests 6. Coastal Dunes and Foreshore

figure2.3 Percentage of all bird numbers observed within all habitats at the

Brisbane Airport

2.4.2 Bird numbers and distribution by habitat

2.4.2.1 Managed Grasslands

The most numerous species found within the managed grasslands was the

Straw necked ibis comprising 38.34% of all bird numbers recorded within

this habitat. The Fairy martin was the next most numerous (14.21% of total

bird numbers recorded) followed by the Sacred ibis making up 10.23% of

individuals observed in the managed grasslands (Table 2.1).

Managed Grassland

Unmanged Grasslands

Casuarina Plantations

Canal WetlandCommunititesMangrove Forests

Coastal Dunes andForeshore

40%

15%13%

11%

3%

18%


2.4.2.2. Unmanaged Grasslands

The most abundant bird species recorded in the unmanaged grasslands was

the Golden headed cisticola (Cisticola exilis) (30.27%), followed by the Tawny

grassbird (Megalurus timoriensis) (20.07%). The Torresian crow was the

third most numerous bird species found in this habitat (Table 2.1).

2.4.2.3 Casuarina Plantations

Within the casuarinas the most common species observed was the Rufous

Whistler (Pachycephala rufiventris) comprising 28.63% of individuals

recorded. This was followed by the grey fantail (Rhipidura fuliginosa) with

22.35%, and the Torresian crow (12.94%) (Table 2.1).

2.4.2.4 Canal Freshwater Wetland, Sedge and Salt marsh Communities

The most common bird species in these areas were the same as for

unmanaged grasslands with the Tawny grassbird making up 39.79% of all

bird species recorded and the Golden headed cisticola the second most

numerous species at 30.24% (Table 2.1).

2.4.2.5 Mangrove Forests

The Mangrove honeyeater (Lichenostomus versicolor) was the most common

bird species (31.94%) while the Mangrove gerygone was the next most

common in this habitat type (19.44%) (Table 2.1).

2.4.2.6 Coastal Dunes and Foreshore

The most abundant species found within the coastal area was the Silver Gull

(Larus novaehollandiae), comprising 17.45% of all birds recorded. The red


necked stint (Calidris ruficollis) was the second most numerous in this habitat

(14.32%) (Table 2.1).

2.4.3 Species richness

Bird diversity was high in all habitats, with the coastal dunes and foreshore

and the managed grasslands sharing the greatest overall species richness

(Figure 2.4).

Species richness also varied temporally with the managed grasslands and

the coastal dunes and foreshore consistently having the greatest number of

species across the year. (Table 2.2)

Number of species in each habitat was assessed seasonally, showing that

managed grasslands, coastal dunes and foreshore shared the greatest

species richness across all seasons (Figure 2.5).


figure2.4 Number of bird species found in habitats at the Brisbane Airport

table2.2Numbers of bird species observed in each habitat over a yearly

period

JUL 2003

AUG 2003

SEP 2003

OCT 2003

NOV 2003

DEC 2003

JAN 2004

FEB 2004

MAR 2004

APR 2004

MAY 2004

JUN 2004

Managed Grasslands

15

17

12

18

22

15

8

14

16

15

9

10

Unmanaged Grasslands

8

8

7

5

9

15

8

11

8

6

4

6

Casuarina Plantation

5

7

8

8

6

9

4

6

8

4

6

5

Canal Wetland

Communities

7

5

4

8

11

11

3

6

4

4

7

4

Mangrove Forests

5

5

5

6

7

6

8

7

6

4

8

5

Coastal Dunes and Foreshore

9

17

13

19

23

18

14

15

20

10

10

11

0

10

20

30

40

50

60

Mana

ged

Gras

sland

s

Unma

nage

dGr

assla

nds

Casu

arina

Planta

tions

Cana

lWe

tland

Comm

unitie

s

Mang

rove

Fores

ts

Coas

talDu

nes a

ndFo

resho

re

Habitat

Num

ber o

f Spe

cies


figure2.5 Average seasonal species richness for each habitat at the

Brisbane Airport.

2.4.4 Monthly and seasonal bird distribution across habitats

A significant difference was observed in the total abundance of birds present

among each habitat type (2 way ANOVA, d.f. =5,210; F=21.043; p=0.00)

with the managed grasslands and the coastal dunes and foreshore having

significantly higher abundance of birds compared with other habitats (Figure

2.6).

No significant difference was observed in abundance of birds found in all

habitats over the length of a year. (2 way ANOVA d.f. = 11,204; F= 0.456;

p=0.928) (Figure 2.7 a, b, c, d, e, f)

A significant difference was also observed in bird abundance across seasons

however, with managed grasslands showing a greater abundance of birds

during the winter months; coastal dunes and foreshore showing the greatest

abundance of birds in the spring, summer and autumn months compared

02468

101214161820

Man

aged

Gra

ssla

nds

Unm

anag

edG

rass

land

s

Cas

uarin

aP

lant

atio

ns

Can

alW

etla

ndC

omm

uniti

es

Man

grov

eFo

rest

s

Coa

stal

Dun

es a

ndFo

resh

ore

Habitat

Ave

rage

Num

ber

of S

peci

esSummer AutumnWinter Spring


with other habitats. (Figure 2.8)

figure2.6 Difference in number of birds per hectare observed in all habitats

at the Brisbane Airport. (Mean ± SE)

Habitat

ForeshoreMangroves

Canal WetlandsCasuarinas

Unmanaged GrasslandsManaged Grasslands

Bird

Num

bers

100

80

60

40

20

0

-20


figure2.7 Yearly bird abundance in each habitat at the Brisbane Airport

(Mean ± SE)

Managed Grasslands

Month

Jun 2

004

May 2

004

Apr

2004

Mar

2004

Feb 2

004

Jan 2

004

Dec 2

003

Nov 2

003

Oct 2003

Sep 2

003

Aug 2

003

Jul 2

003

Bir

d n

um

be

rs

500

400

300

200

100

0

-100

-200


Month

Jun 2

004

May 2

004

Apr

2004

Mar

2004

Feb 2

004

Jan 2

004

Dec 2

003

Nov 2

003

Oct 2003

Sep 2

003

Aug 2

003

Jul 2

003

Bir

d n

um

be

rs

80

60

40

20

0

-20

-40

-60


Month

Jun 2

004

May 2

004

Apr

2004

Mar

2004

Feb 2

004

Jan 2

004

Dec 2

003

Nov 2

003

Oct 2003

Sep 2

003

Aug 2

003

Jul 2

003

Bir

d n

um

be

rs

20

10

0

-10

Canal Wetland Communities

Month

Jun 2

004

May 2

004

Apr

2004

Mar

2004

Feb 2

004

Jan 2

004

Dec 2

003

Nov 2

003

Oct 2003

Sep 2

003

Aug 2

003

Jul 2

003

Bir

d n

um

be

rs

10

8

6

4

2

0

-2

-4

-6

Mangrove Forests

Month

Jun 2

004

May 2

004

Apr

2004

Mar

2004

Feb 2

004

Jan 2

004

Dec 2

003

Nov 2

003

Oct 2003

Sep 2

003

Aug 2

003

Jul 2

003

Bir

d n

um

be

rs

20

10

0

-10


Month

Jun 2

004

May 2

004

Apr

2004

Mar

2004

Feb 2

004

Jan 2

004

Dec 2

003

Nov 2

003

Oct 2003

Sep 2

003

Aug 2

003

Jul 2

003

Bir

d n

um

be

rs

200

100

0

-100

-200

a. b.

c. d.

e. f.


figure2.8 Seasonal bird abundance in each habitat at the Brisbane Airport

2.4.5 Daily bird abundance

A significant difference was observed in the number of birds present at

different periods of the day with more birds per hectare (2 way ANOVA, d.f. =

2,213; F=11.912; p=0.00), and larger numbers per ten minutes of observation

time, seen during the first three hours of sunlight (2 way ANOVA d.f. =2,213;

F=8.367; p<0.05.) (Figure 2.9 a, b)

0

5

10

15

20

25

30

Habitat

Bird

s/he

ctar

e/ho

ur

WinterSpringSummerAutumn

Man

aged

Gra

ssla

nds

Unm

anag

edG

rass

land

s

Cas

uarin

aP

lant

atio

ns

Can

alW

etla

ndC

omm

uniti

es

Man

grov

eFo

rest

s

Coa

stal

Dun

es a

ndFo

resh

ore


figure2.9 Difference in bird numbers observed during three periods of the

day; a) Number of Birds per hectare; b) Number of birds/ten minutes (Mean ±

SE)

Time of Day

3 Hrs before Sunset3 Hrs over Midday3 Hrs After Sunrise

Bird

s pe

r H

ecta

re

9

8

7

6

5

4

3

2

a.

Time of Day

3 Hrs before Sunset3 Hrs over Midday3 Hrs After Sunrise

Bir

d N

um

be

rs

50

40

30

20

10

0

b.


2.5Discussion

A total of 101 bird species were recorded at Brisbane airport during the

census period. This number is slightly lower than had been reported in

previous surveys that have been conducted at Brisbane airport, e.g. the

Fauna Report, conducted by Lambert and Rehbien in 2003 -2004 . The

difference probably reflects differences in the methodology employed with

only birds that spent time within airport habitats recorded here. �ncidental

sightings of bird species were not included here as they were unlikely to

contribute to an ongoing hazard.

Bird diversity was high in all habitats although not all species can be

considered to be a risk to aircraft. Many species found in the unmanaged

grasslands (eg. Tawny grassbird, Golden headed cisticola); the canal

wetlands (eg. Silver eye - Zosterops lateralis, Chestnut breasted mannikin

- Lonchura castaneothorax); the casuarina plantations (eg. Rufous whistler,

Olive backed oriole - Oriolus sagittatus) and the mangrove forests (eg.

Grey shrike thrush - Colluricincla harmonica, Mangrove honeyeater -

Lichenostomus versicolor) have not been reported to have been involved in

bird-aircraft collisions at Brisbane airport. They are not currently considered

to be hazardous species as their behaviour does not bring them into the

vicinity of aircraft flight paths.

Results of this study show clearly that managed grasslands around the

runways, taxiways and aprons provide suitable habitat for a large range

of bird species. 40 percent of all bird species observed in the study were

recorded in grasslands exhibiting a diverse range of behaviours including

foraging, hunting and roosting. �n addition to largest abundance, the

managed grasslands also showed a high species richness. Thus more bird

species were present in managed grasslands per hectare compared with

other habitats except for the coastal dunes and foreshore.


Although the coastal dunes and foreshore showed a greater diversity of

species, many were only present during the spring and summer months, and

so probably constitute migratory species that spend their spring and summer

period feeding in Moreton Bay. Migratory wader species are not considered

to be a great risk to aircraft at Brisbane airport. Previous bird strike data

show only two instances of bird strike where a tern or sandpiper species was

involved (these instances were not identified to species and so we cannot

be certain that they were indeed migratory species) and there has been one

instance of a strike with a migratory Red-necked stint (Calidris ruficollis).

Fluctuations in bird numbers across the year were not large, even taking into

consideration changes in migratory wader numbers. Thus the majority of

birds observed in any single month were likely to be residents of an area and

therefore to be ongoing users of resources found in the habitats in which they

were observed.

Bird numbers and hence activity levels were highest in the early morning

hours. This has a bearing on the risk attached to many bird species as

the number of aircraft movements is also high during this time period. The

number of aircraft movements is greatest in early morning followed by the

midday and early evening hours (Fig 2.2). Although activity of all bird species

was highest during the early morning, many species may not pose hazards to

aircraft. A bird species hazard index is required therefore, before assigning

relative risk to particular times of the day.

This study shows clearly that managed grasslands support the greatest

abundance of bird numbers and species. Further analysis here therefore

should focus on determining which bird species pose potential hazards in

relation to birdstrikes. Subsequently the habitat(s) that contain the greatest

abundance and diversity of potentially hazardous birds over time need to be

identified.

40 Chapter 3. Hazard index for Brisbane Airport habitats

3. AbirDHAZArDinDeXforoPerAtionAlAnDsUrroUnDinGHAbitAtsofbrisbAneAirPort

3.1introduction

Most airports need to reduce the risk of bird strikes in and around the airport

environment. This is usually carried out by performing risk assessments that

identify areas and habitats where major bird hazards occur. Management

can then be concentrated on these areas and control applied to reduce costs

of management and to increase saftey levels.

�dentifying where hazards can be found in the airport environment is only

the first step to correctly identifying where effort to reduce risk should be

concentrated. When directing effort to reduce bird strike potential at airports,

many different issues need to be considered. All bird species may pose a

risk to aircraft, but not all species may be equally hazardous. Factors such

as species, density, location and individual species behaviour need to be

taken into account before determining the relative threat individual species

pose to aircraft (Allen 2000).

As noted earlier, larger and heavier birds are greater potential hazards to

aircraft because they can cause more damage compared with smaller, lighter

birds (Milsom 1990). �t is also accepted that the higher the relative bird

density, the greater will be the hazard to aircraft (Sodhi 2002). An index for

bird hazards at the Brisbane aiport should be based on weight and number

of hazardous birds that are present within and surrounding the airport

environments.

�n order to establish which habitat(s) at the Brisbane airport contain the

greatest number of potentially hazardous birds, an assessment of previous

41Chapter 3. Hazard index for Brisbane Airport habitats

bird strike data and bird presence at Brisbane airport is required to identify

areas that offer the greatest potential for bird strikes.

A bird strike reporting system operates at Brisbane airport, that not only

reports strikes noticed by security staff or aircraft staff, but includes

reports from ground staff when unexplained bird remains are found on,

or surrounding, runways and taxiways. This bird strike data set will be

used here to determine which bird species pose threats to aircraft at the

Brisbane airport. Once specific hazardous species have been identified, this

can be combined with data presented earlier to identify areas that contain

the greatest numbers of these species. �n order to allow monitoring and

comparison in further years, all hazardous species will be indentified, and

then the top ten hazardous species (based on weight and numbers) will

be the major focus. This will enable effort to be directed at reducing bird

strike potential according to a weighted scale from greatest to least hazard

potential for both bird species and habitat type.

3.2Aims

(1) To assess previous bird strike data to determine bird species that pose

the greatest hazard to aircraft at Brisbane airport and to develop a

bird hazard index focusing on species that are of greatest concern at

Brisbane airport.

(2) To identify habitat types at Brisbane airport that contain the greatest

abundance of hazardous bird species.

(3) To provide recommendations for new scientifically based management

options for areas that contain the greatest bird hazard to aircraft.


3.3Methods

3.3.1 Study area

For a description of the study area please see section 2.3.1

3.3.2 Habitat description

See Section 2.3 for description of habitats

3.3.3 Hazard ranking data compilation

Hazard ranking of bird species found at the Brisbane Airport was based on

previous bird strike data (BAC pers comm.) and combined weights of all

birds involved in aircraft collisions (Searing 2001). The mean weight of all

bird species observed, were obtained from Dunning (1992), or an average

of male and female weight were taken if separate weight estimates were

provided for individual sexes of a certain species. �f bird strike data were not

specific and reports only cited to family, then the average weight of all birds

observed in that family was used. For bird species that were not identified an

average weight of all birds involved in aircraft strikes for the same month at

the Brisbane Airport was used.


3.4results

3.4.1 Hazardous bird presence at Brisbane airport

Hazardous bird species were determined from previous bird strike data

collected between 1996 and 2003 (BAC Database). All bird species

previously involved in aircraft collisions were identified as a potentially

hazardous species. Of the 101 species identified as using the entire

Brisbane airport on a regular basis (Appendix 1), 37 individual species were

classed as hazardous to aircraft based on bird strike data records for the

Brisbane airport from 1996-2003. These species were grouped into family or

left as individual species, depending on the specificity of bird strike data.

Each species was given a hazard ranking based on a: the weight of each

species involved in aircraft strikes and b: the total number of each species

previously involved in aircraft collisions. Table 3.1 identifies bird species

that have been involved in aircraft collisions from 1996-2003 and also those

responsible for bird strikes in 2003 alone, and their relative hazard rating.

Note that unidentified (unknown) bird species that have been involved in

aircraft strikes have also been given a hazard rating but were disregarded for

the top ten specific hazardous bird species rankings.

3.4.2 Monthly and seasonal hazardous bird abundance and distribution

Managed grasslands contained the greatest number of hazardous birds with

mangrove forests having the lowest abundance. (Figure 3.1)

Number of hazardous birds observed in each habitat type differed

significantly (F=62.863; d.f. =5, 210; p=0.00) with managed grasslands

having the greatest number followed by the coastal dunes and foreshore.

Other habitats were not significantly different from each other (Figure 3.2).


Note (Table 3.1)

A. Hazard ranking by weights of birds struck

B. Hazard ranking by number of Birds Struck

62%

3%

8%

5%

0%

22%Managed Grasslands



Canal WetlandCommunitiesMangrove Forests

Coastal Dunes andForeshore

figure3.1 Percentage of hazardous birds observed in all habitats on and

around the Brisbane Airport

Species

Strikes

2003

Weight g

Strikes 1996-2003

Weight g

Hazard Ranking

A

Hazard

Ranking B

Nankeen Kestrel Lapwing Spp Swallow Spp/ Martin Spp Egret Spp Torresian Crow Duck Spp Other Raptor Spp Bittern Spp Heron Spp Pigeon Spp Sparrow Spp Royal Spoonbill Common Starling Tern Spp Ibis Spp Magpie Lark White Breasted Sea Eagle Australian Magpie Cormorant Spp Goose Spp Finch Spp Gull Spp Galah Owl Spp Rainbow Lorikeet Red -Necked Stint Sandpiper Spp Unknown Strikes By Other Animal Spp

10 7 4 2 2 2 2 1 1 1 1 1 1 1 - - - - - - - - - - - - -

31 12

1750.00 2653.00 51.80

1150.00 866.00 1719.50 1229.40 360.00 387.50 200.00 34.25

1735.00 82.30 472.50

- - - - - - - - - - - - -

122911.1 N/A

95 27 22 16 7 6 22 5 17 9 10 1 5 2 26 9 6 3 3 3 3 2 1 1 1 1 1

111 44

16625.00 10233.00 284.90 9200.00 3031.00 5158.50 13523.84 1800.00 6587.50 1800.00 342.50 1735.00 411.50 945.00

46800.00 801.00

15828.00 942.00 3511.50 6210.00 48.00 646.00 330.00 451.50 122.00 25.00 74.20

44010.39 N/A

3 6 23 7 12 10 5 13 8 13 21 13 20 15 1 17 4 16 11 9 26 18 22 19 24 27 25 2

N/A

2 3 5 7 10 11 5 12 6 9 8 15 12 14 4 9 11 13 13 13 13 14 15 15 15 15 15 1

N/A

table3.1 Bird strike data, weights and hazard ranking for bird species found

at the Brisbane Airport


Habitat

Bird

s nu

mbe

rs p

er h

ecta

re

10

8

6

4

2

0

-2

ForeshoreMangroves

Canal Wetlands



Managed Grasslands

figure3.2 Hazardous birds observed in each habitat at the Brisbane Airport:

(Mean ± SE)

No significant difference was observed in the total number of hazardous birds

(2 way ANOVA F=0.565; d.f. =2, 204; p=0.856) and the number of birds per

hectare (2 way ANOVA F=0.277; d.f. = 2,204; p=0.990) observed during each

month of the year (Figure 3.3).

When bird numbers were averaged over seasons, the managed grassland

showed a greater abundance of hazardous birds across all four seasons

(Figure 3.4).


3.4.3 Daily hazardous bird abundance

Time of day did not have a significant effect on the number of hazardous bird

species observed at the Brisbane Airport. (2 way ANOVA F=2.504; d.f. =2,

213; p=0.084)(Figure 3.5).

3.4.4 Top ten hazardous bird species and distribution

�n order to focus control and/or management options to reduce the bird strike

hazard at Brisbane airport, we focussed on the top ten ranked hazardous bird

species (Table 3.1). These top ten ranked hazardous species were all found

in a variety of habitats (Figure 3.6). (NB the unknown species that ranked

one for number struck and two for weight of birds struck were not taken into

account for the hazardous species, as the focus needed to be on known

species in order to develop management options). �bis, kestrel, lapwing and

egret species were more abundant in managed grasslands; sea eagles and

other raptor species utilised the canal wetland communities more extensively

than other habitats, while coastal dunes and foreshore had the greatest

abundance of heron, duck and cormorant species. The final hazardous

species, Torresian crow, was recorded in all habitats although the greatest

numbers were observed in the casuarina plantations.

NB. The goose was omitted from the final hazardous species list because

during the bird census, there was no record of a goose species utilising

airport habitats.


Month

Jun 04

May 04

Apr 04

Mar 04

Feb 04

Jan 04

Dec 03

Nov 03

Oct 03

Sep 03

Aug 03

Jul 03

Bird

Num

bers

per

hec

tare

10

8

6

4

2

0

-2

a.

figure3.3 Number of hazardous birds observed over a yearly period at the

Brisbane Airport: Number of birds per hectare (Mean ± SE)


050

100150200250300350

Man

aged

Gra

ssla

nds

Unm

anag

edG

rass

land

s

Cas

uarin

aP

lant

atio

ns

Can

alW

etla

ndC

omm

uniti

es

Man

grov

eFo

rest

s

Coa

stal

Dun

es a

ndFo

resh

ore

Habitat

Bird

Num

bers Summer

AutumnWinterSpring

figure3.4 Average seasonal hazardous bird abundances for each habitat at

the Brisbane Airport.

Time of Day

3 Hrs Before Sunset3 Hrs Over Midday3 Hrs After Sunrise

Bird

s O

bser

ved

40

30

20

10

0

figure3.5 Number of hazardous birds observed during the day. (Mean ±

SE)


figure3.6 Top ten hazardous bird species (based on weight) and habitats in

which they are found at the Brisbane Airport.

a. Ibis Sp

0.001.002.003.004.005.006.007.00

Mana

ged

Gras

sland

s

Cana

lW

etlan

dCo

mmun

ities

Mang

rove

Fore

sts

Coas

talDu

nes a

ndFo

resh

ore

Bird

s/Hec

tare

/Hou

r

b.

Kestrel

0.000.020.040.060.080.100.120.140.16

ManagedGrasslands

UnmanagedGrassslands

Canal WetlandCommunities

Bird

s/Hec

tare

/Hou

r

c. Sea Eagle

0.000.010.020.030.040.050.060.070.08

CasuarinaPlantations

Canal WetlandCommunities

Coastal Dunesand Foreshore

Bird

s/Hec

tare

/Hou

r

d. Raptor sp

0.000.050.100.150.200.250.300.350.400.45

Man

aged

Gra

sslan

ds

Unm

anag

edG

rass

sland

s

Cana

lW

etlan

dCo

mm

unitie

s

Coas

tal

Dune

s an

dFo

resh

ore

Bird

s/He

ctar

e/Ho

ur

e. Lapw ing Sp

0.16

0.17

0.18

0.19

0.20

0.21

Managed Grasslands Coastal Dunes andForeshore

Bird

s/Hec

tare

/Hou

r

f.

Egret sp

0.000.050.100.150.200.250.300.350.400.450.50

Man

aged

Gra

ssla

nds

Unm

anag

edG

rass

slan

ds

Can

alW

etla

ndC

omm

unitie

s

Man

grov

eFo

rest

s

Coas

tal

Dune

s an

dFo

resh

ore

Bird

s/He

ctar

e/Ho

ur

g. Heron sp

0.000.020.040.060.080.100.12

ManagedGrasslands

MangroveForests

Coastal Dunesand Foreshore

Bird

s/Hec

tare

/Hou

r

h.

Duck sp

0.000.200.400.600.801.001.201.401.60

Man

aged

Gra

sslan

ds

Unm

anag

edG

rass

sland

s

Man

grov

eFo

rest

s

Coas

tal

Dune

s an

dFo

resh

ore

Bird

s/Hec

tare

/Hou

r

i. Cormorant sp

0

0.1

0.2

0.3

0.4


Bird

s/Hec

tare

/Hou

r

j. Torresian Crow

0.000.100.200.300.400.500.600.700.80

Man

aged

Gra

ssla

nds

Unm

anag

edG

rass

slan

ds

Cas

uarin

aP

lant

atio

ns

Can

alW

etla

ndC

omm

uniti

es

Man

grov

eF

ores

ts

Coa

stal

Dun

es a

ndF

ores

hore

Bird

s/H

ecta

re/H

our


3.5Discussion

Results of the study show clearly that managed grasslands around the

runways, taxiways and aprons provide suitable habitat for a great range of

bird species. 40 percent of all bird numbers (from all habitats) observed

in the study were recorded in managed grasslands (see Chapter 2) and

exhibited a diverse range of behaviours including foraging, hunting and

roosting. Of the species recorded in managed grasslands, 62 percent of

these species were deemed to be hazardous or to pose a potential risk to

aircraft based on previous bird strike data.

3.5.1 Hazardous bird presence at the Brisbane airport

Bird diversity was high in all habitats (see Chapter 2), although not all

species were considered to be a risk to aircraft. Many species found in the

unmanaged grasslands, the canal wetlands, the casuarina plantations and

the mangrove forests are not known to have been involved in bird-aircraft

collisions at Brisbane airport and are therefore not considered currently to be

hazardous species.

Based on previous bird strike data the top ten bird species that pose the

greatest risk to aircraft are listed in table 3.1. Potential for a catastrophic bird

strike rises with individual size/weight and number of birds struck. The larger

and heavier the bird and the greater number of birds struck in one instance,

the greater is the hazard of damage (Milsom 1990) or abortion of take off and

hence loss of capital. Previous bird strike data at the Brisbane airport has

shown that the majority of bird strikes have involved only a single individual

(87% pers comm BAC). �t is because of these facts that estimates of bird

risk at Brisbane airport have been based, in the first instance, on size and

weight of individual bird species, and secondly on their relative abundance.


Ranking of known hazardous bird species, identified Ibis as the greatest

risk to aircraft at Brisbane airport. �bis utilise grassland around the runways,

taxiways and aprons more extensively and in greater numbers than any other

habitat within the airport boundaries. The fact that ibis also congregate in

relatively large numbers makes their hazard potential far greater than bird

species that do not flock to the same extent.

Austalian kestrels pose the second greatest hazard at Brisbane airport. This

species has been involved in the most aircraft strikes at Brisbane airport

but is ranked second most hazardous because it weighs significantly less

than ibis. Kestrels were also seen in greatest numbers in the managed

grasslands but also occur in unmanaged grasslands and canal wetland

communities to a lesser extent.

Based solely on individual weight of bird species colliding with aircraft, the

White breasted sea eagle poses the greatest potentail damage hazard to

aircraft. This species however has been involved in aircraft strikes only

six times between 1996-2003. White breasted sea eagles utilise the canal

wetland communities far more extensively than any other habitat. During the

point counts, a white breasted sea eagle nesting site was discovered at the

airport that appears to be reused every year for rearing juveniles. Removal

of the nest should reduce the threat posed by this species.

Other raptor species were ranked fourth greatest hazard risk to aircraft,

they were generally observed in greater numbers in the canal wetland

communities. Raptors may use this area for foraging and hunting over the

rank grasslands. Some raptor species were also observed nesting within

eucalypts adjacent to airport boundaries. �n order to reduce raptor numbers,

nesting opportunities need to be reduced where possible.


Other species that have been involved in aircraft strikes, (Lapwing and Egret

species) were observed in greatest numbers in the managed grasslands.

The most common behaviour observed was that of foraging, feeding and

breeding (in the case of the lapwings), indicating that these areas may

afford greater prey availability and other prefered habitat requirements than

alternative habitats around the airport.

Heron, duck and cormorant species were observed in greatest abundance

in the coastal dunes and foreshore areas. �nvolvement of these species

in aircraft strikes may result from them utilising airport airspace simply as

a transit route from one preferred area to another. �n order to reduce the

likelihood of a strike, bird hazing tactics (scaring) that are used at Brisbane

airport should be kept in place to deter these species.

The Torresian crow, although at the lower end of the hazard scale, is the

one species observed in all habitats within the airport boundaries. Reducing

the numbers of this species may require more than habitat manipulation or

removal of observed attractants. Crows utilise the casuarina plantations

for a variety of behaviours, mostly perching and resting within the tops of

the casuarinas, but were rarely seen there foraging or feeding. So while

casuarinas are considered to be a poor fauna habitat for most species,

they still appear to supply a vital resting area for the tenth most hazardous

species of bird (Torresian crow) at Brisbane airport. �n order to reduce the

abundance of Torresian crows, deterrent techniques should be implemented.

3.5.2 Monthly and seasonal abundance of hazardous birds at Brisbane

airport

Data showed that relative abundance of hazardous bird species remained

basically constant across the year. When each habitat type was analysed

separately, managed grasslands showed the greatest abundance of


hazardous species during the winter months (June, July and August) and

the lowest presence of hazardous bird species during the summer period

(December, January and February). Management and control of hazardous

species will thus require greater effort to be employed during the winter

months within the managed grasslands at Brisbane airport.

Coastal dunes and the foreshore showed the greatest abundance of

potentially hazardous species during the autumn months (March, April and

May). This is most likely due to the appearance of migratory wader species

using the area for feeding before migration to breeding grounds during the

winter period. Other habitats within the airport boundaries did not show great

variation in hazard potential across seasons.

While total bird abundance did vary across the day as a whole (See chapter

2), abundance of hazardous birds was constant. Thus bird control efforts

directed against hazardous species need to be maintained throughout

the whole day, not just during peak activity periods for birds or aircraft

movements.

3.5.3 Limitations on hazard ranking

A large number of bird strikes at Brisbane airport have occurred without

records having been made of the actual species involved. When bird

weights are averaged the hazard index of these unknown strikes is relatively

high (Rank 2, see table 3.1). �n order to properly rank these strikes and

to determine their potential hazard, greater effort needs to be directed at

correct identification of bird species involved in strikes in the future. This

may be done by sending remains of unidentified birds to specialists, in order

to have them properly identified. Larger bird species involved in strikes

have a greater chance of being noticed and reported, whereas strikes

involving smaller birds, that may not inflict any damage to the aircraft often


go unnoticed or are not reported. Consistent and correct reporting of all

birdstrikes must be instigated if efforts to reduce bird strike risk are to be

effective in the future.

3.5.4 Habitat hazard ranking and bird reduction recommendations

3.5.4.1 Hazard rank 1 - Managed grasslands

• Managed grasslands around the taxiways and aprons contain the

greatest abundance of bird species, both in number and hazard

potential to aircraft and should be the area where the greatest control

and hazard reduction activities should be focused.

• The management of these grasslands will be addressed later

(Chapter 4).

3.5.4.2 Hazard rank 2 - Coastal dunes and foreshore

• Although the coastal dunes and foreshore provide many requirements

for most hazardous bird species, no major manipulation of the dunes

or mudflats is planned and techniques to deter bird species from

utilising the airport as a movement corridor between habitats need to

be investigated and employed.

• Reduction of perching opportunities (eg. emergent trees) for bird

species should be undertaken.

• Management of the stretch of grassland along the foreshore will be

addressed later (Chapter 4).


3.5.4.3 Hazard rank 3 - Casuarina plantations

• These areas provide poor habitat requirements for the majority of

hazardous bird species. The Torresian crow and the White breasted

sea eagle were the only two hazardous bird species that utilised these

areas regularly.

• Reduction in White breasted sea eagle numbers may be achieved by

monitoring this species and investigating options for either reducing

nesting opportunities or relocating existing nesting areas within the

airport boundaries.

• The Torresian crow utilises casuarina plantations extensively, but

even the removal of these areas (for example when construction of

the new runway begins) will not necessarily reduce their numbers

as they have been observed to utilise all available habitats at the

airport. To reduce abundance of crows hazing of this species should

be increased, and new options for deterring this species should be

trialed.

3.5.4.4 Hazard rank 4 - Canal freshwater wetland, sedge and salt marsh

communities

• The canal freshwater wetland, sedge and salt marsh communities

are similar to those of the unmanaged grasslands within the

operational areas of the airport, and these areas provide hunting

and roosting opportunities for many hazardous bird species. These

areas should also be managed to reduce habitat requirements for

hazardous species. Uunmanaged grasslands were the focus of

habitat manipulation experiments in Chapter 4 so recommendations


for bird control effort in these areas will be discussed later.

3.5.4.5 Hazard rank 5 - Unmanaged grasslands

• Although unmanaged grasslands provide few of the basic habitat

requirements for hazardous bird species in the original bird risk

assessment, they were involved in the experiments currently being

undertaken on the managed grasslands, and recommendations for

control of these areas will be discussed in Chapter 4.

3.5.4.6 Hazard rank 6 - Mangrove forests

• Hazardous bird species were low within mangrove forests and no

manipulation or bird reduction efforts is considered necessary in

these habitats, currently.

3.5.5otherrecommendations

• �n order to increase the accuracy of bird species hazard ranking

and to provide a more detailed bird strike data base, records of bird

strikes must correctly identify all individual birds involved in aircraft

collisions.

57Chapter 4. Grassland management strategy to reduce bird strikes

4. AcosteffectiveGrAsslAnDMAnAGeMentstrAteGYtoreDUcetHenUMberofbirDstriKesAtbrisbAneAirPort

4.1introduction

Bird strikes are an escalating problem at many airports, so much so that

bird species, their abundance and activity around airports are a major

focus when assessing risk to aircraft movements (Allen 2000; Allen et al.

2003). Habitat management achieved by modification of vegetation present

within airport boundaries combined with use of bird dispersal techniques

have been regarded as some of the most effective long term management

options for reducing bird numbers at airports. (Solman 1969; Burger 1983;

Buckley & McCarthy 1994; Brown et al. 2001; Byron & Downs 2002) Studies

into the effectiveness of maintaining long grass as a bird deterrent have

demonstrated that grass heights between 15 and 45 cm can deter bird

species such as gulls and lapwings (Brough & Bridgman 1980; Buckley &

McCarthy 1994) while this approach is not as effective for other species

such as Canadian geese (Seamans & Dolbeer 1999). While many airports

have adopted a long grass policy as a part of their ongoing bird strike risk

management, this option must be tailored to each specific location to account

for difference in bird species, vegetation types, food resource availability and

local environmental conditions.

A previous bird risk assessment undertaken at Brisbane airport (Chapter 3)

has identified Ibis (Threskiornis aethiopica and T. spinicollis), the Australian

kestrel (Falco cenchroides), raptor species (Black shouldered kite Elanus

axillaris, Whistling kite Haliastur sphenurus, White breasted sea eagle

(Haliaeetus leucogaster), Masked lapwing (Vanellus miles) and Egret species

58 Chapter 4. Grassland management strategy to reduce bird strikes

(Great egret Egretta alba, �ntermediate egret Egretta intermedia, Little egret

Egretta garzetta and Cattle egret Ardea ibis) to be the major bird threats to

aircraft safety.

Chapter 2 and 3 of this study identified managed grasslands as the habitat

providing greatest threat of birdstrike at Brisbane airport.

The objective of this study was to develop a cost effective and

environmentally acceptable grass height management strategy that can be

applied to the managed grasslands of the Brisbane airport to reduce potential

hazard of bird strikes.

4.2Methods

4.2.1 Study area

See Section 2.3.1

All sites for grassland manipulation trials were chosen within maintained

areas, and grass left to grow for three months prior to the study. Three

geographically separate areas ranging from 7.7 hectares in area 1, 14.3

hectares in area 2 and 11.0 hectares in area 3, were chosen for the study

(Figure 4.1a)

4.2.2 Prior to Manipulation

4.2.2.1 Vegetation structure

The areas selected for this study were chosen in locations that had been

analysed previously for vegetation diversity in a flora and fauna survey (ERM


figure4.1 a) Grassland management study areas within Brisbane Airport

Boundaries. b) Site A. c) Site B. d) Site C.

(Each site broken into 4 areas of equal size and randomly allocated a

treatment height)

a.

b.c.

d.


2002) and shown to support similar vegetation diversity. Three sites (Figure

4.1 b. c. d.) were divided into four areas of equal size for manipulation of

grass heights. Prior to manipulation, twenty random points were selected

in each of the 12 areas and grass height measured at each point using the

direct method (measuring height of sward) (Stewart et al. 2001).

4.2.2.2 Bird utilisation

Prior to manipulation, bird utilisation within the twelve sites was determined

on a single occasion (April 2004) by surveying bird use over a forty minute

period, during three daily periods: three hours after sunrise; three hours over

the midday period; and three hours before sunset. Each forty minute period

was broken into 10 four minute surveys, and all birds seen and heard within

the designated area and their activity, were recorded for each four minute

period. Birds flying over the areas were not included unless behaviour

clearly showed that the area was being utilised (eg. hunting). Bird surveys

were restricted to days when weather conditions did not interfere with the

detections of birds, eg rain, and excess wind and fog (Ralph et al. 1993).

4.2.3 Grassland Manipulation

Four areas were assigned randomly within each geographic site to a different

grass height treatment (Figure 4.1 b,c,d):

Treatment were;

1. 0-10cm grass height;



4. >50cm grass height.


Grass height treatment 1 is the current grassland maintenance program

practised at Brisbane airport. The second and third grass treatment heights

were chosen on the basis of the seeding heights of the most abundant grass

species identified (ERM 2002) that were known to be utilised by birds as a

food resource (Barker & Vestjens 1940). The fourth treatment was where

grassed areas were left to grow without maintenance. A week before each

bird observation, grass height was determined at each site as described

previously and if grass was over the designated treatment height, the site

was slashed to reduce grass height to within the desired limits. The time

taken for the manipulation at each site was recorded as was the type of

equipment (tractor type) used and amount of fuel consumed to complete site

maintenance.

4.2.4 Food Resources

4.2.4.1 �nvertebrate Resources

Surface dwelling invertebrates were sampled monthly using pitfall traps (285

mL plastic cups containing 120 mL of propylene glycol, placed into holes in

the ground to bring the lip of the cup level with the ground). Pitfall traps were

place in each treatment in each of the 3 geographically separate locations

(Figure 4.1). 10 Pitfall traps were placed along a transect through the centre

of each treatment, each 20 metres apart. Pitfall traps were left for 7 days

(unless there was rain during the period then each pitfall was checked and

emptied every day during rain). All trapped invertebrates were counted and

identified to Order.

Foliar invertebrates were sampled monthly using a sweep net. Ten

standardised sweeps were taken through the tops of the vegetation over a 10

metre transect and samples preserved in containers with propylene glycol,


counted and identified to Order.

4.2.4.2 Vertebrate Resources

Small vertebrates that could be utilised by birds as a food resource were also

captured in pitfall traps, but were not targeted specifically for capture as the

bird species identified as the greatest hazard at the Brisbane airport did not

rely on this resource as a primary food resource (Barker & Vestjens 1940).

4.2.4.3 Seed Resources

Samples of grass seed were taken monthly by randomly placing 10, 1m x

1m quadrats in each treatment type. All grass seed known to be a likely food

resource (Barker & Vestjens 1940) for hazardous birds at Brisbane Airport

were collected, sorted into species, dried and weighed.

4.2.5 Economic analysis

All manipulations of grass height treatments were recorded by Airport

maintenance staff, detailing date and time taken to complete the

maintenance. Cost of maintenance included cost of fuel, and wages of

maintenance crew. Fuel was priced at average price of diesel fuel for the

month during which maintenance was carried out, and wages were priced at

award rates for maintenance staff at Airports within Australia.

4.2.6 Statistical Analysis

For analysis, bird utilisation at each site is reported as relative bird

utilisation/1.9 hectares/40mins, reflecting the size of the smallest site and the

searching time.


During the grass height manipulation phase of the study (June 2004-May

2005 except Dec 2004 due to rain), grass height and bird utilisation were

determined each month using the methods described previously.

For analysis, bird species were classified as either potentially hazardous or

non hazardous. This classification was based on previous bird strike data

collected between 1996 and 2003 (BAC pers comm.) with all bird species

previously involved in aircraft collisions identified as potentially hazardous.

This resulted in 37 species classified as potentially hazardous to aircraft

(Appendix 2).

4.3results

4.3.1 Prior to grassland manipulation

Prior to manipulation, the 12 areas selected for study here (4 areas in each

of 3 geographic sites) were unmanaged grasslands with similar vegetation

consisting of Bunchy Sedge (Cyperus polystachous), White Clover (Trifolium

repens), Common Plantain (Plantago lanceolata), Narrow Leaf Carpet

Grass (Axonopus fissifolius), Rhodes Grass (Chloris gayana), Couch Grass

(Cynodon dactylon), Red Natal Grass (Melinis repens), Paspalum (Paspalum

dilatum), Bahia Grass (Paspalum notatum), Kikuyu Grass (Pennisetum

clandestinum), Rats Tail Grass (Sporobolus indicus) (ERM 2002) and Buffalo

Grass (Stenotaphrum secundatum). Vegetation structure of the 12 sites

were similar with a mean vegetation height of 60.7cm ± 1.3 cm (Figure 4.2).

Bird utilisation was also assessed at all sites on a single occasion (April

2004) prior to manipulation. A total of 196 birds were observed over the

12 sites (Table 4.1), and of this number 49% (96 birds) were categorised

potential hazards to aircraft (BAC pers comm.). Prior to manipulation,

utilisation by all birds at all sites was similar (Figure 4.3 a) as was utilisation


by potentially hazardous birds (Figure 4.3 b).

figure4.2 Mean vegetation height (± SE) for all areas before manipulation.

The solid and dotted lines represent the mean ± 95% Confidence interval of

vegetation height of all sites, n=20 for each site.

Site B

121110987654321

Mea

n gr

ass

heig

ht (c

m)

75

70

65

60

55

50

Site A Site C


table4.1 Non hazardous and potentially hazardous birds observed in each

site before manipulation.

SPECIES SITE 1 2 3 4 5 6 7 8 9 10 11 12

Non hazardous species Golden headed cisticola Tawny grass bird Willy wagtail Richards pipit

6 4 0 0

4 2 0 0

2 2 0 0

2 1 2 3

4 3 0 3

3 2 0 4

9 0 0 1

7 0 0 4

7 0 0 2

5 0 0 3

5 0 0 0

10 0 0 0

Total non hazardous birds 10 6 4 8 10 9 10 11 9 8 5 10 Potentially hazardous species

Fairy martin Welcome swallow Cattle egret Intermediate egret Australian kestrel Torresian crow Whistling kite Chestnut teal Pacific black duck

0 1 1 1 3 0 0 0 0

0 0 1 3 3 0 0 0 0

5 2 0 0 0 0 0 0 0

4 1 0 1 0 0 0 0 0

0 0 0 0 2 4 0 0 0

0 0 0 0 2 3 1 0 0

2 5 0 0 2 0 1 1 1

1 5 0 0 2 0 1 1 0

4 0 0 0 1 0 0 0 0

4 0 0 0 1 0 0 0 0

11 0 0 0 2 0 0 0 0

11 0 0 0 2 0 0 0 0

Total hazardous birds 6 7 7 6 6 6 12 10 5 5 13 13 Total Birds 16 13 11 14 16 15 22 21 14 13 18 23


figure4.3 Relative bird utilisation (birds observed/1.92ha/40min) at all

sites prior to manipulation: a. All bird species; b. Potentially hazardous bird

species.

The solid and dotted lines represent the mean ± 95% confidence interval of

bird utilisation of all sites.

a.

Sites

121110987654321

Rel

ativ

e bi

rd u

tilis

atio

n 20

15

10

5

0

b.

Sites

121110987654321

Rea

ltive

bird

util

isat

ion

20

15

10

5

0


4.3.2 Grassland manipulation

Grass height was maintained within the desired treatment parameters (Figure

4.4) over the period June 2004-May 2005. This required 11, 8, 6 and 0

manipulations of the 0-10 cm, 10-30cm, 30-50cm and >50cm treatments,

respectively (Table 4.2).

figure4.4 Mean grass height (± SE) during vegetation manipulation for

each treatment over the period June 2004-May 2005.

Treatment 1: 0-10 cm (X), treatment 2:10-30cm (O), treatment 3: 30-50cm

(∆), treatment 4: >50cm (□), n=12 for each month.

* Denotes months that manipulation was undertaken. n = 3 for each

treatment

Month

May 05Apr 05Mar 05Feb 05Jan 05Nov 04Oct 04Sep 04Aug 04Jul 04Jun 04

Mea

n gr

ass

heig

ht (c

m)

100

80

60

40

20

0


table4.2 Mean grass height (± SE) for each treatment over the course of

the study

* Denotes months when manipulations were necessary.

Over the course of the study, total bird utilisation varied greatly among sites

(Table 4.3). Areas with the current Airport management practice of repetitive

mowing to keep grass in the 0-10cm range had the highest overall bird

utilisation levels (Figure 4.5 a). �n contrast, lowest overall bird utilisation

occurred in sites where grass height was maintained in the 30-50cm range

(2 way ANOVA F=18.0 d.f = 3,132 P<0.001) (Figure 4.5 a). This trend

persisted across all months of the study (Figure 4.5 b), where, in each month,

areas employing the current management practice had the highest or equal

highest utilisation. �n every month, areas where grass height was maintained

in the 30-50cm range had lowest utilisation by total birds (2 way ANOVA

F=18.0 d.f = 3,132 P<0.001).

Month Treatment 1 Treatment 2 Treatment 3 Treatment 4

Jun 2004

Jul 2004

Aug 2004

Sep 2004

Oct 2004

Nov 2004

Jan 2005

Feb 2005

Mar 2005

Apr 2005

May 2005

6.4±0.5 *

7.6±0.6 *

7.0±0.4 *

8.8±1.3 *

6.5±0.5 *

7.1±0.4 *

6.5±0.4 *

7.2±0.4 *

7.0±0.4 *

7.3±0.3 *

7.0±0.3 *

17.9±0.7 *

18.2±0.7

15.6±0.7 *

17.4±0.9 *

16.4±0.7 *

18.5±0.6

18.1±0.6 *

15.4±0.4 *

15.8±0.3 *

18.9±0.4

18.4±0.5 *

34.7±0.6 *

37.3±1.0

31.7±1.1

34.3±1.0 *

35.1±0.7 *

34.1±0.5

33.8±0.5 *

35.1±0.7 *

34.9±0.4 *

37.0±0.5

34.6±0.4

72.5±2.8

71.0±3.1

68.6±2.8

69.1±2.6

70.0±2.8

66.4±3.2

76.0±3.1

71.2±3.0

75.1±2.8

67.8±2.4

68.4±3.0


table4.3 Relative bird utilisation (birds/1.92ha/40mins) of treatment type (x

± SE) for hazardous, non hazardous and all bird species over the period of

the study.

Month Species Treatment (Grass height)

0-10cm 10-30cm 30-50cm >50cm

Hazardous 23.8±7.0 (8) 3.2±2.0 (5) 1.4±0.7 (3) 3.8±2.4 (4)

Non hazardous 13.1±4.2 (2) 12.8±5.1 (2) 0.9±0.7 (2) 6.4±1.9 (2) Jun-04 Total 36.9±9.6 16.1±5.4 2.3±0.9 10.2±2.6

Hazardous 66.0±53.3 (5) 2.9±1.6 (5) 4.1±3.7 (3) 1.3±0.5 (3)

Non hazardous 9.5±2.0 (2) 9.0±4.3 (1) 1.1±0.7 (1) 4.0±1.8 (2) Jul-04 Total 75.5±53.3 11.9±5.2 5.2±3.8 5.3±1.8

Hazardous 41.3±30.9 (4) 33.0±24.5 (4) 5.0±2.3 (3) 4.8±2.0 (3)

Non hazardous 22.5±7.9 (3) 8.3±4.5 (1) 0 14.9±7.3 (1) Aug-04 Total 63.8±28.8 41.3±23.7 45.0±2.3 19.7±7.5

Hazardous 24.0±7.3 (4) 8.1±1.8 (6) 1.0±0.9 (3) 10.5±6.1 (3)

Non hazardous 11.5±3.1 (2) 6.8±2.5 (1) 0.1±0.1 (1) 17.7±3.7 (3) Sep-04 Total 35.5±9.2 14.9±3.4 1.1±0.9 28.2±6.0

Hazardous 27.6±6.6 (8) 22.9±6.6 (8) 4.6±1.9 (4) 11.2±5.5 (3)

Non hazardous 20.2±2.4 (2) 20.2±2.4 (1) 0.2±0.2 (1) 23.8±5.2 (1) Oct-04 Total 47.8±7.8 47.8±7.8 4.8±1.9 35.0±8.3

Hazardous 20.7±5.7 (9) 9.1±3.1 (8) 7.6±5.7 (2) 2.8±1.3 (4)

Non hazardous 16.2±3.1 (2) 11.7±2.7 (1) 2.1±1.6 (1) 26.1±3.8 (2) Nov-04 Total 36.9±7.3 20.8±2.4 9.8±5.5 28.8±4.3

Hazardous 67.9±17.4 (10) 27.6±10.6 (7) 15.1±10.7 (5) 24.3±17.0 (3)

Non hazardous 18.4±2.5 (1) 10.6±2.2 (1) 2.2±1.6 (2) 31.6±5.2 (2) Jan-05 Total 86.3±18.3 38.2±10.1 17.4±10.7 56.2±19.3

Hazardous 10.4±5.6 (7) 3.1±1.5 (4) 1.0±0.7 (3) 3.5±2.5 (4)

Non hazardous 23.0±4.3 (1) 8.8±2.2 (1) 0.2±0.1 (1) 36.1±7.0 (2) Feb-05 Total 33.4±5.3 12.0±3.2 1.2±0.7 39.7±6.6

Hazardous 21.1±4.5 (6) 35.3±19.8 (9) 3.3±1.8 (4) 0.7±0.4 (4)

Non hazardous 28.4±5.5 (3) 13.8±4.3 (1) 0 21.4±3.5 (2) Mar-05 Total 49.5±6.8 49.0±23.4 3.3±1.8 22.1±3.5

Hazardous 37.9±8.5 (7) 27.7±5.9 (7) 10.1±2.2 (3) 4.3±1.8 (3)

Non hazardous 23.3±4.6 (2) 21.3±4.2 (2) 0 26.2±4.9 (1) Apr-05 Total 61.2±9.9 48.9±7.4 10.1±2.2 30.5±5.0

Hazardous 77.1±24.8 (9) 78.2±18.7 (10) 7.6±3.9 (5) 6.5±2.4 (3)

Non hazardous 21.8±3.8 (2) 21.8±5.4 (1) 0 21.4±3.9 (1) May-05 Total 98.9±25.2 100.0±18.5 7.6±3.9 27.9±3.7


figure4.5 (a) Total relative bird utilisation (birds observed/1.92ha/40mins)

within each treatment over the period of the study (b) Total monthly relative

bird utilisation (birds observed/1.92ha/40mins) within each treatment

(X-0-10cm, O-10-30cm, ∆-30-50cm, □->50cm)

a.

Treatment

>50cm30-50cm10-30cm0-10cm

Rel

ativ

e bi

rd u

tilis

atio

n (m

ean±

SE)

200

180

160

140

120

100

80

60

40

20

0

-20

b.

Month

May05Apr05

Mar05Feb05

Jan05Nov04

Oct04Sep04

Aug04Jul04

Jun04

Rel

ativ

e bi

rd u

tilis

atio

n (m

ean±

SE) 140

120

100

80

60

40

20

0

-20


Similar utilisation patterns were observed for potentially hazardous birds.

Over the course of the study, areas that employed the current Airport

management practice (Treatment 1) supported significantly higher utilisation

whereas sites maintained in the 30-50cm and >50cm height ranges

supported the lowest utilisation (F= 10.48 d.f = 3,132 P=<0.001) (Figure 4.6

a). On a monthly basis, the trend was similar to that for all birds but was

not as marked. Areas employing the current management practice also

supported the highest utilisation with areas maintained within the 30-50cm

and >50cm ranges supporting the lowest utilisation (F=10.87 d.f=3,132

P<0.001) (Figure 4.6 b).

Bird utilisation, by both total and hazardous species, varied across the year

with highest utilisation occurring in July 2004, January 2005 and May 2005 in

areas that employed the current management practice. �n contrast utilisation

of areas maintained in the 30-50cm range were not only low, but were

consistently low over all sampled months.

Not only was total number of birds singnificantly lower in areas in the

30-50cm and >50cm height range treatments, so to were the number of

potentially hazardous species. 18 hazardous species were observed at

areas employing the current management practice compared with 13 and

10 species in areas maintained in the 30-50cm and >50cm grass height

categories, respectively (Table 4.4).

Compared with the current management practice, maintenance of grass

height within a 30-50cm height range reduced total bird utilisation by 89.2%

and utilisation by potentially hazardous birds was reduced by 85.4%.

Time of day had a significant effect on utilisation, with highest utilisation by

both all bird species and potentially hazardous bird species occurring in the

three hours after sunrise (Figure 4.7 a, b). This period also corresponds with

the period of highest aircraft movement (Figure 4.8)


figure4.6 (a) Total relative bird utilisation of potentially hazardous bird

species (birds observed/1.92ha/40mins) within each treatment over the

period of the study (b) Total monthly utilisation of potentially hazardous bird

species (birds observed/1.92ha/40mins) within each treatment

(X-0-10cm, O-10-30cm, ∆-30-50cm, □->50cm)

a.

Treatment

>50cm30-50cm10-30cm0-10cm

Rel

ativ

e bi

rd u

tilis

atio

n (m

ean±

SE)

200

180

160

140

120

100

80

60

40

20

0

-20

b.

Month

May05Apr05

Mar05Feb05

Jan05Nov04

Oct04Sep04

Aug04Jul04

Jun04

Rel

ativ

e bi

rd u

tilis

atio

n (m

ean±

SE

) 140

120

100

80

60

40

20

0

-20


table4.4 Utilisation of treatments by bird species.

Percentage of total is given in parentheses. Percentages in total rows

are based on rows and not columns. All other percentages are based on

columns.

TREATMENT SPECIES 0-10cm 10-30cm 30-50cm >50cm

Non Hazardous Bird Species

Black faced cuckoo shrike Coracina novaehollandiae

Brown quail Coturnix pectoralis

Golden headed cisticola Cisticola exilis

Grey plover Pluvialis squatarola

Pied butcherbird Cracticus nigrogularis

Richards pipit Anthus novaeseelandiae

Tawny grass bird Megalurus timoriensis

Willy wagtail Rhipidura leucophyrs

2 (0.2)

4 (0.4)

0

11(1)

12 (1.1)

252 (23)

0

2 (0.2)

0

0

0

0

3 (0.4)

189 (27)

0

0

0

0

1 (0.4)

0

0

15 (5.7)

1 (0.4)

2 (0.8)

0

0

275 (50.7)

0

0

2 (0.4)

23 (4.2)

0

Total non hazardous birds 283 (11.0) 192 (7.5) 19 (0.7) 300 (11.7)

Potentially hazardous species Australian kestrel Falco cenchroides

Australian magpie Gymnorhina tibicen

Black shouldered kite Elanus axillaris

Brown falcon Falco berigora

Cattle egret Ardea ibis

Common starling Sturnus vulgaris

Crested pigeon Ocyphaps lophotes

Fairy martin Hirundo ariel

Great egret Egretta alba

Intermediate egret Egretta intermedia

Little egret Egretta garzetta

Magpie lark Grallina cyanoleuca

Masked lapwing Vanellus miles

Pacific black duck Anas superciliosa

Royal spoonbill Platalea regia

Sacred ibis Threskiornis aethiopica

Straw necked ibis Threskiornis spinicollis

Torresian Crow Corvus orru

Welcome swallow Hirundo neoxena

Whistling kite Haliastur sphenurus

White faced heron Ardea novaehollandiae

11 (1)

31 (2.9)

0

2 (0.2)

11 (1)

54 (5.1)

2 (0.2)

98 (9.2)

1 (0.1)

2 (0.2)

0

195 (18.4)

54 (5.1)

4 (0.4)

2 (0.2)

61(5.8)

217 (20.5)

21 (2)

8 (0.8)

0

3 (0.3)

20 (2.9)

14 (2)

1 (0.1)

2 (0.3)

11 (1.6)

16 (2.3)

3 (0.4)

123 (17.5)

1 (0.1)

1 (0.1)

0

58 (8.3)

66 (9.4)

0

0

3 (0.4)

157 (22.4)

16 (2.3)

7 (1)

1 (0.1)

9 (1.3)

5 (1.9)

0

2 (0.8)

0

10 (3.8)

0

0

113 (42.8)

0

1 (0.4)

1 (0.4)

0

5 (1.9)

1 (0.4)

0

33 (12.5)

48 (18.2)

7 (2.7)

13 (4.9)

0

6 (2.3)

36 (6.6)

0

20 (3.7)

2 (0.4)

0

0

0

141 (26)

0

1 (0.2)

0

0

0

1 (0.2)

0

36 (6.6)

0

0

2 (0.4)

2 (0.4)

1 (0.2)

Total hazardous birds 777(30.3) 509 (19.8) 245 (9.5) 242 (9.4)

Total Birds 1060(41.3) 701(27.3) 264(10.3) 542(21.1)


figure4.7 Relative bird utilisation (bird observed/1.92ha/40mins) of (a) all

bird species; (b) potentially hazardous bird species during the day.

a.

Time of day


Rel

ativ

e bi

rd u

tilis

atio

n (m

ean±

SE)

60

50

40

30

20

10

0

b.

Time of day


Rel

ativ

e bi

rd u

tilis

atio

n (m

ean±

SE)

60

50

40

30

20

10

0


figure4.8 Aircraft movements at Brisbane airport showing peak of

movement over the 8am –9am period of the morning.

(Sunrise in Brisbane varied from 0444-0638hrs over the year) (BAC pers

comm. for July 2003-July2004)

4.3.3 Food Resources for Birds

4.3.3.1 �nvertebrates

Twenty three orders/classes of invertebrates were found in the treatments

(Table 4.5), but length of grass maintenance height did not have a significant

effect on relative abundance of ground dwelling invertebrates (F=1.316 d.f=3,

1444 P=0.267) (Figure 4.9).

Time of day

2200-2259

2000-2059

1800-1859

1600-1659

1400-1459

1200-1259

1000-1059

0800-0859

0600-0659

0400-0459

0200-0259

1200-1259

Num

ber o

f Airc

raft

Mov

emen

ts

35

30

25

20

15

10

5

0


Foliar invertebrates provided similar results to ground dwelling invertebrates

with no significant difference between treatment types (F=1.708 d.f=3, 840

P=0.164) (Figure 4.10).

table4.5 Complete count of invertebrates and vertebrates (Order/Class)

sampled from pitfall traps.

Order/Class Treatment

1 2 3 4

Anura (Frogs) 22 32 18 31Aranae (Spiders) 774 945 885 873Blattodea (Cockroaches) 21 38 25 39Chilopoda (Centipedes) 64 34 59 25Coleoptera (Beetles Weevils Ladybirds) 638 361 407 472Collembola (Springtails) 3754 4134 5552 2240Diplopoda (Millipedes) 0 2 3 0Dermaptera (Earwigs) 5 1 9 10Diptera (Flies, crane flies, mosquitoes, midges, sandflies) 460 307 247 214Gastropoda (Snails) 4 29 153 67Haplotaxida (Earthworms) 55 52 22 22Hemiptera (Bugs, leafhoppers, cicadas, aphids, scale insects) 582 618 421 323Hymenoptera (Ants) 6806 13662 9297 6226Hymenoptera (Wasps) 25 27 22 31Hymenoptera (Bees) 3 0 4 0Isopoda (Isopods) 560 168 291 897Lepidoptera (Moths and butterflies) 82 57 48 7Mantodea (Praying mantids) 2 1 2 4Neuroptera (Lacewings, antlions) 1 0 0 0Odonata (Dragonflies, damselflies) 1 0 0 0Orthoptera (Grasshoppers, locusts, crickets, katydids) 274 292 307 376Phthiraptera (Lice) 2 1 2 0Psocoptera (Booklice, barklice) 6 5 0Rodentia (Mice) 10 1 3 16Squamata (Lizards) 4 12 13 34Trichoptera (Caddisflies) 9 3 6 1

Total 14159 20785 17804 11912

0


figure4.9 Ground dwelling invertebrate abundance for each treatment type.

(Mean ± SE)

figure4.10 Foliar invertebrate abundance for each treatment type. (Mean ±

SE)

±±


4.3.3.2 Vertebrates

As vertebrates were not targeted as a main food resource here, they have

only been included in the table (Table 4.5) as a possible food resource. To

determine if the number of vertebrates within treatments differ, more studies

of vertebrate abundance should be conducted.

4.3.3.3 Seeds

Six species of grass and sedge were identified as possible sources of seeds

for granivorous birds (Table 4.6). There was a significant difference in seed

resources available to all birds (both hazardous and non hazardous) at

Brisbane airport (F=16.436 d.f=3,128 P=<0.000) (Figure 4.11). Treatment

4 showed a significanly higher availability of seeds during seeding seasons,

although the majority of birds that utilised treatment 4 were not considered a

hazard to aircraft. Seed abundance in treatments 1, 2 and 3 were low and

not significanlty different.

4.3.4 Economic Analysis

Mean direct costs associated with maintenance of the 4 grass height

treatments varied considerably (Table 4.7). Compared with the current

practice, maintenance of grass height for the 30-50cm range resulted in a

45% reduction in the number of manipulations required per year (11 to 6)

and a 64% reduction in annual maintenance cost per hectare ($108.86 to

$39.29).

Extrapolating this cost saving to the entire airport where 866.67 hectares of

grassland requires manipulation, maintaining grass height within the 30-50cm

range would result in an annual cost saving of $60, 312 (64%) to the Airport.


table4.6 Dry weights of grass seed species sampled from all treatments.

figure4.11 Dry weight of grass seeds (mean ± SE) collected from

treatments

Speices Treatment1 2 3 4

Paspalum (Paspalum dilatum ) 5.171 71.138 19.274 289.676Bahia Grass (Papalum notatum ) 0 2.314 0 3.567Rats tail grass (Sporobolus indicus ) 0 3.748 4.889 30.552Rhodes grass (Chloris gayana ) 0 3.716 11.037 438.968Marine couch (Sporobolus virginicus ) 0 0 0 6.742Sedge (Cyperus polystacyous ) 0 0 0.193 107.694Total 5.171 80.916 35.393 877.199

±


table4.7 Mean direct costs ($/ha) associated with the maintenance of the

various grass height treatments based on actual fuel cost ($12-14 per litre),

manipulation time, maintenance costs and salary costs ($22.16/hr).

Treatment 0-10cm 10-30cm 30-50cm >50cm

June 2004

$7.43 $2.48 $8.90 $0.00

July 2004

$11.11 $0.00 $0.00 $0.00

August 2004

$3.25 $2.89 $0.00 $0.00

September 2004

$16.82 $6.63 $3.69 $0.00

October 2004

$8.15 $2.58 $2.86 $0.00

November 2004

$11.11 $0.00 $0.00 $0.00

January 2005

$6.49 $3.23 $8.35 $0.00

February 2005

$10.79 $14.55 $8.61 $0.00

March 2005

$11.89 $5.57 $6.87 $0.00

April 2005

$7.33 $0.00 $0.00 $0.00

May 2005

$14.50 $13.12 $0.00 $0.00 TOTAL $108.86 $51.06 $39.29 $0.00


4.4Discussion

Birds (especially the Australian kestrel and �bis species) present an ongoing

major hazard to aircraft operations at Brisbane airport even though a

continual bird hazing program is conducted there. Chapters 2 and 3 of

this thesis demonstrated that the greatest bird hazard is associated with

grasslands that surround operational areas. The significance of the ongoing

problem is not surprising given that this habitat comprises 32% of the total

area of the airport and greatest utilisation of this habitat by birds occurs

during the three hours after sunrise, a period that corresponds with highest

intensity of aircraft movements. The problem is further exacerbated by the

high diversity of potentially hazardous bird species that utilise this habitat

compared with total bird diversity (18/29 species). Obviously, an additional

management component is needed if the potential risk associated with bird

presence is to be reduced to an acceptable level.

Habitat utilisation by vertebrate species results from organism-resource

interactions. Management of vertebrates can therefore be approached

from two conceptually different directions that are based on; either the

manipulation of the organism (direct mortality, forced movement etc)

or manipulation of the resources provided by the habitat. �t is generally

accepted that manipulation of resources provide the greatest chance of

success as this approach attempts to remove resources that give rise to

the problem rather than trying to cope with the problem once it has arisen.

�n the case of Brisbane airport, given the high diversity of hazardous bird

species, management of vegetation resources that support bird populations

rather than management of specific bird species, would be the preferred

management option here.

Utilisation of a vegetation type by birds is a function of vegetation structure


and the amount and type of food available. Vegetation with a low vertical

structure may offer some bird species a wide expanse of uninterrupted

vision thus also reducing predation risk (Devereux et al. 2004). Grass that is

mown regularly may also disturb invertebrates and vertebrates, allowing bird

species to use less energy when foraging for food.

Vegetation management, particularly the implementation of the “long grass

policy” (Mead & Carter 1973) is a common method employed at many

airports to deter potentially hazardous birds species from utilising airport

grounds for resources. The effectiveness of this approach in reducing bird

presence at airfields has been demonstrated on British airfields for species

such as gulls, lapwings, Corvids and Golden plover (Pluvialis apricaria)

(Brough & Bridgman 1980). Other airports around the world have also

demonstrated the effectiveness of habitat modification to reduce presence

of Magpie larks (Grallina cyanoleuca) (Crossfield 2001) and laughing gulls

(Larus atricilla) (Buckley & McCarthy 1994).

Although this approach has been successful in reducing the abundance of

some bird species, it may not be effective for all species. A study into the use

of tall grass to reduce number of Canadian geese (Branta Canadensis) at

airports in Canada was unable to demonstrate that this approach is effective

at reducing bird utilisation levels (Seamans & Dolbeer 1999).

Foraging behaviour and relative success may also be altered when habitat

modifications are made. For some species that use visual acuity to detect

food, increasing the structural complexity of grasslands in which they forage,

can reduce relative detectability of prey and therefore also reduce foraging

success (Butler & Gillings 2004). An increase in grass sward height can also

affect foraging mobility by impeding movement in grasslands, and produce a

reduction in foraging rates (Butler & Gillings 2004).


Similarly, shorter swards and less structurally complex grasslands may

improve foraging rates, for soil and surface invertebrate feeders. This may

result from increased food accessability, a reduction in predator risks and

a reduction in mobility costs (Vickery et al. 2001; Whittingham & Markland

2002; Atkinson et al. 2004; Devereux et al. 2004; Whittingham & Evans 2004;

Atkinson et al. 2005).

Vegetation with a highly developed structure can also reduce prey visibility

for bird species that rely on dive hunting and also increase their chance of

damage when dive or perch hunting.

�t is therefore not surprising that vegetation management has been effective

at reducing potential for bird strikes at many airports around the world.

Unfortunately, success of vegetation management varies, as utilisation by

birds is a function of bird and vegetation diversity and local environmental

conditions. Complexity of these interactions means that it is extremely difficult

to extrpolate outcomes of previous studies to every new situation.

�n this study, existing grasslands were manipulated by regular slashing to

provide: low vertical structure/low food supply of seeds (0-10cm height),

moderate vertical structure/low food supply of seeds (10-30cm height), high

vertical structure/low food supply of seeds (30-50cm height) and maximum

vertical structure/high food supply of seeds (>50cm height). Compared with

the current management practice (0-10cm height), maintenance of grass

height within a 30-50cm height range provided greatest reduction in bird

hazard potential. This management option resulted in a reduction of total

bird utilisation by 89% while utilisation by potentially hazardous species

was reduced by 85%. Reduced hazard potentials were consistent across

the year. �n addition, utilisation by �bis species was consistently low across

the year compared with current management practices and utilisation by

the Australian kestrel was lower in this treatment than in the >50cm height


treatment. Not only was total utilisation by all bird species reduced in the

30-50cm height treatment, so to were the number of potentially hazardous

species (13 species compared with 18 species in the 0-10cm height

treatment).

Utilising a grass management regime to effectively reduce the number

of birds that were previously abundant, must however, not provide new

resources or present new niches that may be exploited by other bird species.

Maintenance of grass height to within a 30-50cm height did not provide an

increased abundance of ground dwelling or foliar invertebrates, compared

with that in other treatments. Maintaining sward height within a 30-50cm

range was also shown to reduce the abundance of grass seed as a food

resource for granivorous species.

Maintaining grass height within a 30-50cm height range also provides a

significant economic advantage over the current management practice with

the number of manipulations required annually being reduced by 45% (11 to

6) and a subsequent direct cost saving per hectare of 64%. �f extrapolated

to the entire area of grasslands requiring manipulation within the airport,

maintenance of grass height within a 30-50cm range results in an annual

saving of over $60,000 to Airport management.

�n summary, this study has shown that the maintenance of grass height within

a 30-50cm range is a cost-effective management option that will significantly

reduce the potential hazard due to bird strikes at Brisbane airport. This

management option (Appendix 3) can be applied to any area of the Brisbane

airport that is regularly maintained including the managed grasslands within

the operational areas; and the managed strips of grassland along the coastal

dunes and foreshore.

Optimisation of hazard potential reduction will rely on studies that investigate


the effect of particular vegetation species that could replace the existing mix

of grasses and an understanding of the relative importance of vegetation

structure and food supply in determining utilisation by potentially hazardous

bird species.

86 Chapter 5. General discussion/Conclusions

GenerAlDiscUssion

Birdstrikes are considered to be a major threat to aircraft safety. Because

of this, risk assessments are a common occurrence when it comes to

determining the hazards associated with birds and the risk they pose to

aircraft. As all airports are different, and airport environments often support

different bird species, risk assessments should be tailored to each airport

separately.

Brisbane airport has a unique environment and the potential for individual

bird species, that utilise this area for resources may vary in their potential to

pose a threat to aircraft and therefore passenger safety. The airport consists

of 6 major habitats that surround the major runways and taxiways. An

investigation of each of the major habitats in detail showed that the managed

areas (grasslands that are continually maintained at a short sward length)

around the runway and taxiways contain the greatest abundance of bird

species.

According to previous bird strike data recorded at the Brisbane airport, not all

species that were observed in all habitats were considered a hazard or risk

to aircraft, as many species had not been recorded to have been involved in

aircraft strikes. The results of the bird strike analyses showed similar results

to the risk assessment and identified managed grasslands to be the habitat

at the Brisbane airport that consistently housed the highest density of bird

secies and numbers that were assessed as posing a threat to aircraft.

Management plans have been implemented at many airports around the

world to reduce birdstrike risk. One such approach is the manipulation of

existing vegetation to preclude many bird species. �n order to determine if

this general management option would transfer successfully to the Brisbane

87Chapter 5. General discussion/Conclusions

airport, managed grasslands at the airport were subjected to an experimental

manipulation of grass sward height. This management option combined

experimental strategies from other airports around the world, and resulted

in a new grassland management strategy for Brisbane. Maintaining grass

swards within the managed area of the Brisbane airport at a length of 30-

50cm, reduced total number of birds and the number of hazardous birds that

utilised grass areas for food and other resources significantly. Maintenance

of grass swards within this height range was also shown not to increase the

availability of invertebrate or seed resources for bird species.

Managing grasslands at a 30-50cm height range also reduced the number

of times grasslands at the Brisbane airport had to be maintained over a year,

leading to significant savings on fuel, and salary costs.

These are important findings for the Brisbane airport as not only are airport

management adhering to strict risk assessment procedures to ensure aircraft

safety, they are also striving to make the airfield a non-preferred environment

for bird species, without resorting to depredation of species.

Allowing grass swards to remain at a longer height than previous

maintenance regimes reduced bird numbers significantly. This outcome

reflects outcomes of studies at other airports around the world. Most

notably Mead and Carter (1973), Brough and Bridgman (1980), Buckley and

McCarthy (1994), found that using long grass as a management strategy,

deterred some bird species from utilising critical areas at specific airports.

Most previous studies of bird presence and grass height interactions at

airports have not investigated resource availability or other organism

resource interactions. Even though the results achieved from experiments

at Brisbane airport were similar to other studies around the world, more

research into organism resource interactions within airport surroundings


could provide better information on reasons for initial bird presence. While

lower numbers of hazardous birds were found to utilise the longer grassed

areas (30-50cm) during this study, the driving factors were not identified here.

There are many potential explanations as to why presence of long grass

may reduce bird numbers. Longer grass may; impede mobility for some bird

species, may reduce line of sight and therefore increase predation risk of

some bird species; and reduce success of foraging within longer grass due

to greater energy costs associated with detection of prey. Conversely longer

grass may increase the availability of invertebrate and seed resources and

allow cover for some bird species that improves their relative reproduction

success. Although many studies into vegetation management at airfields

have been conducted, most have concentrated on presence and absence

of birds as evidence that a particular management strategy has succeeded

or failed. This inferred relationship could be strengthened by studying the

availability of resources and assess the ability of organisms to determine

resource availability.

Environmental factors that could affect prey density/diversity such as

temperature and weather were not taken into consideration here. Results

of the food resources study may have been affected by other factors.

Maintenance of grass heights could have disturbed more insects in the low

grass treatments, that in turn could have affected invertebrate numbers within

pitfall traps. The likelihood of this was kept to a minimum however, with bird

censusing occurring at least two days after maintenance of grass heights had

been carried out.

�t is also not known whether vegetation species, structure and complexity

will remain the same over an extended time period under a particular

maintenance regime. The maintenance of grass at a certain height over

time may favour the growth of a particular species more than others that

may exclude some species that are present now. Any change in vegetation

89Chapter 5. General discussion/Conclusions

structure may also have an effect on the types and abundance of food

resources for birds that in turn could alter the bird species present and

therefore affecting the types of species utilising the managed grassland

habitat.

Research into the success of a establishing a single monoculture of a

grass species over the entire airfield could also produce different results

to experimentation carried out over an airfield with multiple grass species.

There has been some research that has shown that agricultural grassland

with low sward diversity and structural complexity may reduce invertebrate

fauna diversity and abundance and in turn reduce the number of birds that

utilise this area for food resources (Vickery et al 2001) . Although this has not

been applied to airfields to date this could be a direction for future research at

Brisbane airport.


conclUsions

�n order to reduce potential for birdstrike at the Brisbane airport, maintenance

of grasslands around the runways and taxiways should be kept at a height of

30-50cm (see appendix 3). This will reduce numbers and possibly diversity

of hazardous species. Maintenance of grass at a height of 30-50cm will also

reduce cost of habitat maintenance significantly.

�nitiation of maintenance of grass to a height of 30-50cm, will not however

reduce bird numbers to zero and so there still remains a need for constant

surveillance and harassing of birds that are present. While bird numbers

should be reduced after implementation of this grassland management

option, monitoring of the management option should be ongoing in order to

determine if the strategy continues to be successful.

91Appendices

Bird Species

1

2

3

4

5

6

Quails, Pheasants – Family Phasianidae Brown quail Coturnix pectoralis X X X

Pelicans – Family Pelecanidae Australian pelican Pelecanus conspicilatus X

Darters – Family Anhingidae Australian darter Anhinga melangaster X

Cormorants – Family Phalacrocoracidae Pied cormorant Phalacrocorax fuscescens X Little pied cormorant Phalacrocorax varius X Little black cormorant Phalacrocorax carbo X

Ducks – Family Anatidae Pacific black duck Anas superciliosa X X X X X Chestnut teal Anas castanea X X

Rails – Family Rallidae Lewin's rail Rallus pectoralis X

Herons, Egrets, Bitterns – Family Ardeidea White faced heron Ardea novaehollandiae X X X X X Cattle egret Ardea ibis X X Great egret Egretta alba X X Little egret Egretta garzetta X X X Intermediate egret Egretta intermedia X X Mangrove (striated) Heron Butorides striatus X X Black bittern Ixobrychus flavicollis X

Ibises, Spoonbills – Family Plataleidae Sacred Ibis Threskiornis aethiopica X X X X Straw necked ibis Threskiornis spinicollis X X X X Royal spoonbill Platalea regia X X

Curlews, Sandpipers, Godwits – Family Scolopacidae Eastern Curlew Numenius madagascariensis X Little Curlew Numenius minutes X Whimbrel Numenius phaeopus X Common Sandpiper Actitis hypoleucos X Curlew Sandpiper Calidris ferruginea X Marsh Sandpiper Tringa stagnatilis X Sharp Tailed Sandpiper Calidris acuminata X X Terek sandpiper Tringa terek X Bar tailed godwit Limosa lapponica X Black tailed godwit Limosa limosa X Grey tailed tattler Tringa brevipes X Red necked stint Calidris ruficollis X X Red knot Calidris canutus X X Sanderling Calidris alba X Common greenshank Tringa nebularia X

X

APPenDices

Appendix1 Species identified as present within habitats

92 Appendices

Bird Species

1

2

3

4

5

6

Oystercatchers – Family Heamatopodidae Pied oystercatcher Heamatopus longirostris X

Lapwings, Plovers – Family Charadriidae Masked lapwing Vanellus miles X X Mongolian (lesser) sand plover Charadrius mongolus X Double banded plover Charadrius bicinctus X Lesser golden plover Pluvialis dominica X Red-capped plover Charadrius ruficapillus X Greater (large) sand plover Charadrius leschenaultii X

Stilts, Avocets- Family Recurvirostridae Black winged stilt Himantopus himantopus X

Gulls, Terns – Family Laridae Silver gull Larus novaehollandiae X Caspian tern Hydropogne caspia X Gull billed tern Sterna nilotica X

Osprey – Family Panidionidae Osprey Pandion haliaetus X X X

Kites, Goshawks, Eagles, Harriers – Family Accipitridae Black shouldered kite Elanus notatus X X Brahminy kite Haliastur indus X X Whistling kite Haliastur sphenurus X X Brown Goshawk Accipiter fasciatus X White-breasted sea eagle Haliaeetus leucogaster X X X Spotted Harrier Circus assimilis X Swamp harrier Circus approximans X

Falcons – Family Falconidae Brown falcon Falco berigora X Nankeen (Australian) kestrel Falco cenchroides X X X

Pigeons, Doves – Family Columbidae Crested pigeon Ocyphaps lophotes X Bar shouldered dove Geopelis humeralis X

Cockatoos – Family Cacatuidae Galah Cacatua roseicapilla X

Lorikeets – Subfamily Loriinae Rainbow lorikeet Tricholglossus haematodus X

‘Broad Tailed Parrots’ – Subfamily Playtcercinae Pale headed rosella Platycercus adscitus X

Kingfishers – Family Alcedinidae Collared kingfisher Halcyon chloris X Forest kingfisher Halcyon macleayii X

Kookaburra XDacelo novaeguineae

Appendix1 Species identified as present within habitats (Continued)

93Appendices

Bird Species

1

2

3

4

5

6

Bee Eaters – Family Meropidae Rainbow bee-eater Merops ornatus X X

Rollers – Family Coraciidae Dollar Bird Eurystomus orientalis X

Fairy Wrens – Family Maluridae Red-backed fairy wren Malurus melanocephalus X X X

Gerygones – Family Pardalotiae Brown gerygone Gerygone mouki X X Mangrove gerygone Gerygone levigaster X

Honeyeaters – Family Meliphagidae Brown Honeyeater Lichmera indistincta X Fuscous honeyeater Lichenostomus fuscus X Lewin’s honeyeater Meliphaga lewinii X Varied (mangrove) honeyeater Lichenostomus versicolor X Striped Honeyeater Plectorhyncha lanceolata X White eared honeyeater Lichenostomus leucotis X Yellow faced honeyeater Lichenostomus chrysops X Noisy Miner Manorina melanocephala X

Shrike Thrushes, Whistlers – Family Pachycephalidae Grey shrike thrush Colluricincla harmonica X X Rufous whistler Pachycephala rufiventris X

Magpie Larks, Flycatchers, Fantails, Drongo – Family Dicruidae Magpie-lark Grallina cyanoleuca X Leaden flycatcher Myiagra rubecula X Grey fantail Rhipidura fuliginosa X X Willy wagtail Rhipidura leucophyrs X X X X Spangled drongo Dicrurus bracteatus X

Orioles – Family Oriolidae Olive backed oriole Oriolus sagittatus X

Cuckoo-shrikes – Family Campephagidae Black faced cuckoo shrike Coracina novaehollandiae X

Butcherbirds – Family Artamidae Grey butcherbird Cracticus torquatus X Pied Butcherbird Cracticus nigrogularis X Australian magpie Gymnorhina tibicen X

Crows – Family Corvidae Torresian crow Corvus orru X X X X X X

Swallows, Matins – Family Hirundinidae Welcome swallow Hirundo neoxena X X X X Fairy martin Hirundo ariel X X X X Tree martin Hirundo nigricans X X


94 Appendices

Bird Species

1

2

3

4

5

6

Pipits – Family Motacillidae Richard’s pipit Anthus novaeseelandiae X

Warblers – Family Sylviidae Clamorous reed warbler Acrocephalus stentoreus X X Golden headed cisticola Cisticola exilis X X X Tawny grassbird Megalurus timoriensis X X X Little grassbird Megalurus gramineus X X

Mannikins – Family Ploceidae Chestnut breasted mannikin Lonchura castaneothorax X X

White Eyes – Family Zosteropidae Silver eye Zosterops lateralis X Mistletoe bird Dicaeum hirundinaceum X

Starlings, Mynas – Family Sturnidae Common starling Sturnus vulgaris X


Note: Habitats

1 - Managed Grasslands

2 - Unmanaged Grasslands

3 - Casuarina Plantations

4 - Canal Wetland and Sedge Communities

5 - Mangrove Forests

6 - Coastal Dunes and Foreshores

95Appendices

Bird species Bird Strikes 2004

Bird Strikes 1996-2004

Unknown Family Accipitridae

- Black shouldered kite (Elanus axillaris) - Brahminy kite (Haliastur indus) - Whistling kite (Haliastur sphenurus) - White breasted sea eagle (Haliaeetus leucogaster)

Family Anatidae - Duck sp - Goose sp

Family Ardeidea - Black bittern (Ixobrychus flavicollis) - Egret sp - White faced heron (Ardea novaehollandiae)

Family Artamidae - Australian magpie (Gymnorhina tibicen)

Family Cacatuidae - Galah (Cacatua roseicapilla)

Family Charadriidae - Masked lapwing (Vanellus miles)

Family Columbidae - Crested pigeon (Ocyphaps lophotes)

Family Corvidae - Torresian crow (Corvus orru)

Family Dicruidae - Magpie-lark (Grallina cyanoleuca)

Family Falconidae - Australian kestrel (Falco cenchroides) - Brown falcon (Falco berigora)

Family Hirundinidae - Swallow/Martin sp

Family Laridae - Silver gull (Larus novaehollandiae) - Tern sp

Family Panidionidae - Osprey (Pandion haliaetus)

Family Passeridae - Sparrow sp

Family Phalacrocoracidae - Cormorant sp

Family Plataleidae - Royal spoonbill (Platalea regia) - Ibis sp

Family Ploceidae - Finch sp

Family Psittacidae - Rainbow lorikeet (Tricholglossus haematodus)

Family Scolopacidae - Red-necked stint (Calidris ruficollis) - Sandpiper sp

Family Sturnidae - Common starling (Sturnus vulgaris)

Family Tytonidae - Owl sp

11 (3) 2 1 1 1

(1) - -

(8) 2 - - 7 - 1 5

12 -

(3) - - -

(1)

(1) -

(4) - - 2

(4) 1

(1)

41 (13)

3 2 1 6

(13) (2)

5

(21) 18 3 2

29

10 7

13

102 3

(42)

11 (2)

1

(12)

(3) 1

(35)

(14) 1 2

(4) 7

(2)

Appendix2 Bird stikes

96 Appendices

Appendix3 Grassland Management Strategy

Airfield Grassland Maintenance Present and Future

The Brisbane airports present grassland management: (0-10cm length)

• Provides many bird species (eg lapwings, starlings, magpie larks,

magpies, crows) with an increased foraging success due to easy

detection of food resources

• Allows bird species free movement and an increased security due to

early visual detections of approaching danger

• Frequent mowing provides grassland with a built up humus layer that

is an ideal environment for invertebrates which in turn attract certain

bird species

• Frequent mowing disturbs invertebrates allowing easy detection of

prey for both hazardous and non hazardous bird species

The recommended change to management of grass to a length of 30-50cm:

• May reduces foraging success due to reduction in ability to detect

prey

• May reduce foraging mobility by impeding movement thru grasslands

• Detection of impending danger may be reduced as view is obstructed

by complex grass structure

• Long grass management (30-50cm) at Brisbane airport will preclude

many bird species (magpies, magpie larks, starlings, pigeons, and

lapwings) all of which are considered to be a potential bird strike risk.

• Reduces numbers of Corvids and some species of waders

97Appendices

Principles of Long Grass Management

Management of all grassed areas at the Brisbane airport (excepting all areas

around signs and lights) at a length of 30-50cm, should take into account the

following requirements:

• No increase in fire hazards

• No FOD (Foreign Object Damage) hazard accumulation

• Cutting of grass must not be left too late so as to have long (100-

150mm) grass lying on top of the sward, as this may become

FOD hazard, encourage insects which attract birds, and kill grass

underneath which encourages weed infestation.

• Easy access by emergency vehicles

• Emergency access roads, Runway end safety areas, unpaved stop

ways, and graded areas of runways and taxiway strips must not be

concealed by long grass. �n these areas grass should be cut to a

maximum height of 200mm.

• Runway lights, precision approach path indicators, marker boards, etc

must not be obstructed

• The grassed areas around lights and signs should be cut short so as

to increase visibility, where as grassland around �nstrument landing

systems may be grown longer (200mm)

98 Appendices

The Management System

(Adapted from Deacon and Rochard 2000)

figureA.1 Grassland management regime for Brisbane airport.

�n early September (early spring) grass needs to be cut short and all

old growth, excess vegetation and accumulated clippings and humus

layer removed. This will stimulate rapid regrowth during the spring and

encourage grasses to flower by the end of spring (Nov) which will ensure

strong stems that will allow the sward to be supported throughout the winter

months. As this cutting of the grassland will leave vegetation short and stir

up invertebrates, increased vigilance and bird hazing practices need to be

employed during the establishment of strong healthy grass swards.

It may not be necessary to apply this first cut and removal of excess

vegetation every year, a healthy grass sward may be maintained by following

this spring regime every two to three years depending on the vegetation

500 450

400 350

300 250 200

150 100

50 0

Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Month

Gra

ss h

eigh

t (m

m)

Grass Cutting accumulation (not to scale)

Clearing c c c = Grass cut c c

99Appendices

present.

Any raking, clearing, rolling, spraying of weeds and fertilising of grass swards

should be carried out during the spring period.

The first cut to ensure the swards remain between 30 and 50cm, should

be carried out after most grasses have flowered. As most of the grasses

at Brisbane airport flower and seed between 300 and 500 mm, it is not

necessary to let the grass sward grow to the full 500mm extent before the

first cut. Cutting height should be set with the maintenance machines on the

grass, rather than on a hard surface.

Further cuts should be repeated each time the grass height reaches between

400-500mm. Further cuts will be necessary at least every month during the

late spring and summer months.

No further cuts are necessary after growth ends in autumn (late May early

June).

Any introduction of a new maintenance regime must be monitored and

adapted for each specific airfield and both the maintenance crew and the

bird control crew must be closely involved in the planning, monitoring and

evaluation of the maintenance program.

100 References

references

Airforce U. S. (1997) Bird Aircraft Strike Hazard (BASH) Management

Techniques. Department of the United States Airforce.

Allen J. R. (2000) A Protocol for Bird Strike Risk Assessment at Airports.

�n: Proceedings of the 25th �nternational Bird Strike Committee,

Amsterdam.

Allen J. R. (2002) The cost of birdstrikes and birdstrike prevention. �n: Human

conflicts with wildlife: Economic considerations. (ed. C. L) pp. 147-153.

National Wildlife Research Centre, Fort Collins, Colorado USA.

Allen J. R. & Orosz A. P. (2001) The costs of birdstrikes to commercial

aviation. �n: Bird Strike 2001.

Allen J. R., Orosz A. P., Badham A. & Bell J. (2003) The development of

birdstrike risk assessment procedures, their use on airports, and the

potential benefits to the aviation industry. In: Proceedings of the 26th

�nternational Birdstrike Committee, Warsaw, Poland.

Atkinson, P.W., Buckingam, D. and Morris, A.J. (2004) What factors

determine where invertebrate-feeding birds forage in dry agricultural

grasslands? �bis. 146 : (Supp 2) 99-107.

Atkinson P. W., Fuller R. J., Vickery J. A., Conway G. J., Tallowin J. R.,

Smith R. E. N., Haysom K. A., Ings T. C., Asteraki E. J. & Brown V. K.

(2005) Influence of agricultural management, sward structure and food

resources on grassland field use by birds in lowland England. Journal of

Applied Ecology. 42: 932-942.

101References

ATSB (2002) The Hazard Posed to Aircraft by Birds pp. 48. Australian

Transport Safety Bureau, Australian Capital Territory.

Austin-Smith P. J. & Lewis H. F. (1970) Alternative vegetative ground cover.

�n: Proceedings of the World Conference on Bird Hazards to Aircraft, pp.

153-160, Kingston.

BAC (1999) Airport Environment Strategy. Brisbane Airport Corporation. pp

104.

Bailey G. (2000) Bird Strike. �n: Flight Safety Australia pp. 40-43.

Barker R. D. & Vestjens W. J. M. (1940) The food of Australian Birds

Volume 1 & 2. CSIRO Australia.

Barras S. C. & Wright S. E. (2002) Civil aircraft collisions with birds and other

wildlife in Ohio, 1990-1999(1). The Ohio Journal of Science. 102: 2-7.

Barry D. H. (1974) Bird Strikes - a fuller picture of the present situation and

an assessment of the possible effects of the development plan. �n:

Brisbane Airport Development - Project Environment Study - Terrestrial

Study Factor Reports. Brisbane Airport, Brisbane, Australia.

Baxter A. (2000) Use of distress calls to deter birds from landfill sites near

airports. �n: Proceedings of the 25th �nternational Bird Strike Committee,

Amsterdam.

Blokpoel H. (1976) Bird Hazards to Aircraft: Problems and prevention of bird/

aircraft collisions. Clarke, �rwin and Co, Ottowa.

102 References

Blokpoel H, Klaver A, and Burrma L. (2003) The need for an artificial,

bird-unfriendly ground cover for airports. �n: Proceedings of the 26th

�ntenational Bird Strike Committee, Warsaw.

Brough T. (1967) Recent Developments in Bird Scaring on Airfields. In: The

problems of birds as pests. (eds. R. K. Murton & E. N. Wright). Academic

Press, London/New York.

Brough T. & Bridgman C. J. (1980) An evaluation of long grass as a bird

deterrent on British airfields. Journal of Applied Ecology. 17: 243-253.

Brown J. & Hickling G. (2000) The problems of analysis of pilot-reported

bird-strikes as an index for actual bird-strikes at airports. New Zealand

Journal of Zoology 27: 45-47.

Brown K. M., Erwin R. M., Richmond M. E., Buckley P. A., Tanacredi J. T. &

Avrin D. (2001) Managing birds and controlling aircraft in the Kennedy

airport - Jamaica Bay wildlife refuge complex: The need for hard data

and soft opinions. Environmental management 28: 207-224.

Buckley P. A. & McCarthy M. G. (1994) Insects, vegetation, and the control of

laughing gulls (Larus atricilla) at Kennedy �nternational Airport, New York

City. Journal of Applied Ecology. 31: 291-302.

Burger J. (1983) Bird Control at Airports. Environmental Conservation 10:

115-124.

Burger J. (1985) Factors affecting bird strike on aircraft at a coastal airport.

Biological Conservation 33: 1-28.

103References

Busnel R. G. & Giban J. (1967) Prospective Considerations Concerning

Bio-Acoustics in Relation to Bird-scaring Techniques. �n: The problems

of birds as pests. (eds. R. K. Murton & E. N. Wright). Academic Press,

London/New york.

Butler S. & Gillings S. (2004) Quantifying the effects of habitat structure on

prey detectability and accessibility to farmland birds. �bis 146: 123-130.

Byron J. & Downs C. T. (2002) Bird presence at Oribi airport and

recommendations to avoid bird strikes. South African Journal of Wildlife

Research 32: 49-58.

CAA (2002) CAP 680 Aerodrome Bird Control. Civil Aviation Authority,

London.

Carter N. B. (2003) Border Collies Prove Effective in Controlling Wildlife at

Airports. �nternational Civil Aviation Organisation (�CAO) Journal 58: 4-7.

Chilvers B. L., Ryan C. J. & Hickling G. J. (1997) Factors affecting pilot-

reported bird-strike rates at Christchurch �nternational Airport, New

Zealand. New Zealand Journal of Zoology 24: 1-7.

Cleary E. C. & Dolbeer R. A. (1999) Wildlife Hazard Management at Airports.

Federal Aviation Administration and United States Department of

Agriculture wildlife services publication.

Crossfield E. L. (2001) Habitat Preference of the Australian magpie-lark

Granilla cyanoleuca at Adelaide Airport, South Australia. �n: Department

of Environmental Biology. University of Adelaide.

104 References

Cunningham R. B., Lindenmayer D. B., Nix H. A. & Lindenmayer B. D. (1999)

Quantifying observer heterogeneity in bird counts. Australian Journal of

Ecology 24: 270-277.

Deacon N. & Rochard J. B. A. (2000) Fifty years of airfield grass

management in the UK. �n: Proceedings of the 25th �nternational Bird

Strike Committee, Amsterdam.

DeFusco R. P. (2000) Current status of the USAF Bird Avoidance Model.


Amsterdam.

Dekker A. (1996) Birds and Grassland on Airports. �n: Proceedings of the

23rd Bird Strike Committee Europe, London.

Dekker A. (2000) Poor Long Grass: Low bird density ground cover for the

runway environment. �n: Proceedings of the 25th �nternational Bird Strike

Committee, Amsterdam.

Dekker A. (2003) Taking habitat management one step further. �n:

Proceedings of the 26th �nternational Bird Strike Committee, Warsaw.

DeSante D. F. (1986) A Field Test of the Variable Circular-Plot Censusing

Method in a Sierran Subalpine Forest Habitat. Condor 88: 129-142.

Devereux C. L., McKeever C. U., Benton T. G. & Whittingham M. J. (2004)

The effect of sward height and drainage on Common Starlings Sturnus

vulgaris and Northern Lapwings Vanellus vanellus foraging in grassland

habitats. �bis 146: 115-122.

105References

Dolbeer R. A., Belant J. L. & Sillings J. L. (1993) Shooting gulls reduces

strikes with aircraft at John. F. Kennedy �nternational Airport. Wildlife

Society Bulletin 21: 442-450.

Dolbeer R. A., Chipman R. B., Gosser A. L. & Barras S. C. (2003) Does

Shooting Alter Flight Patterns of Gulls to Avoid an Airport: Case Study

at John F. Kennedy �nternational Airport. �n: Proceedings of 26th

�nternational Bird Strike Committee, Warsaw.

Dolbeer R. A., Wright S. E. & Cleary E. C. (2000) Ranking the Hazard Level

of Wildlife Species to Aviation. Wildlife Society Bulletin 28: 372-378.

Dunning J. B. J. (1992) CRC handbook of avian masses. CRC Press, Boca

Raton, FL.

Engeman R. M., Peterla J. & Constantin B. (2002) Methyl anthranilate

aerosol for dispersing birds from the fligth lines at Homestead Air

Reserve Station. �nternational Biodeterioration and Biodegradation. 49:

175-178.

ERM (2002) Brisbane Airport: Vegetation and Condition Assessment pp. 70.

Environmental Resource Management Australia, Pyrmont NSW.

Eschenfelder P. (2001) Wildlife Hazards to Aviation. �n: �CAO/AC� Airports

Conference, Miami, Florida.

Eschenfelder P. (2003) Mandatory Strike Reporting - The Time has Come. �n:


106 References

Fennessy G., Kelly T. C., O’Callaghan M. J. A., Bourke P. D., Sheehy S.

& Bolger R. (2003) Bird aircraft interactions in relation to ambient

light conditions. �n: Proceedings of the 26th �nternational Bird Strike

Committee, Warsaw.

Froneman A. & Van Rooyen M. (2003) The Successful Implementation of

a Border Collie Bird Scaring Program at Durban �nternational Airport,

South Africa. �n: Proceedings of the 26th �nternational Bird Strike

Committee, Warsaw.

Fuller R. J. & Langslow D. R. (1984) Estimating numbers of birds by point

counts: how long should counts last? Bird Study 31: 195-202.

Gunn W. W. H. & Solman V. E. F. (1967) A Bird Warning System for Aircraft

in Flight. In: The problems of birds as pests. (eds. R. K. Murton & E. N.

Wright). Academic Press, London/New York.

Hummel D. J. (1983) Aerodynamic aspects of formation flight in birds.

Theoretical Biology 104: 321-348.

Jacobi V. (1996) Study of Bird Behaviour to Bird Strike Prevention. �n:

Proceedings of 23rd Bird Strike Committee Europe, London.

Kelly T. C., Bourke P. D., O’Callaghan M. J. A., Fennessy G., Bolger R. &

Sheehy S. (2003) The Effect of Length of Daylight on Bird-Strike Rates.

�n: Proceedings of 26th �nternational Bird Strike Committee, Warsaw.

Leshem Y. & Froneman A. (2003) Flight Safety and Nature Conservation

- The ulitmate connection, The Great Rift Valley case study. �n:


107References

Linnell M. A., Conover M. R. & Ohashi T. J. (1996) Analysis of bird strike at a

tropical airport. Journal of Wildlife Management 60: 935-945.

Linnell M. A., Conover M. R. & Ohashi T. J. (1999) Biases in bird strike

statistics based on pilot reports. Journal of Wildlife Management 63:

997-1003.

Lovell C. D. & Dolbeer R. A. (1999) Validation of the United States Air Force

Bird Avoidance Model. Wildlife Society Bulletin 27: 167-171.

Manktelow S. (2000) The effect of weather conditions on bird-aircraft

collisions at British airports. �n: Proceedings of the 25th �nternational Bird


Mead H. & Carter A. W. (1973) The management of long grass as a bird

repellent on airfields. Journal of the British Grassland Society. 28: 219-

222.

Milsom T. P. (1990) The use of Birdstrike statistics to monitor the hazard

and evaluate risk on UK civil aerodromes. �n: Proceedings of the 20th

Birdstrike Committee Europe, Helsinki.

Neubauer J. C. (1990) Why Birds Kill: Cross-Sectional Analysis of U.S Air

Force Bird Strike Data. Aviation, Space and Environmental Medicine.

April: 343-348.

Patterson B. (2000) Wildlife control at Vancouver �nternational Airport:

�ntroducing boarder collies. �n: Proceedings of the 25th �nternational Bird


108 References

Pell S. & Jones D. (2002) Bird numbers and aircraft bird-strike at Brisbane

Airport during 2001, and during the six-year period, 1996-2001. pp. 18.

Griffith University, Brisbane, Australia.

Ralph C. J., Geupel G. R., Pyle P., Martin T. E. & DeSante D. F. (1993)

Handbook of Field Methods for Monitoring Landbirds. General Technical

Report PSW-GTR-144. pp. 41. U.S Department of Agriculture, Forest

Service, Pacific Southwest Research Station., Albany, CA.

Rao A. & Pinos A. (1998) Bird strike threat is best countered by effective

wildlife control augmented by land-use management. �nternational Civil

Aviation Organisation (�CAO) Journal: 5-6.

Reynolds R. T., Scott J. M. & Nussbaum R. A. (1980) A Variable Circular-Plot

Method for Estimating Bird Numbers. Condor 82: 309-313.

Rhodes M. & Jones D. (2004) Bird numbers and aircraft bird-strikes at

Brisbane airport during 2002 pp. 16. Griffith University, Brisbane.

Robbins C. S. (1981) Effect of time of day on bird activity. Studies in Avian

Biology 6: 275-286.

Rosenstock S. S., Anderson D. R., Giesen K. M., Lerkering T. & Carter

M. F. (2002) Landbird counting techniques current practices and an

alternative. The Auk 119: 46-53.

Ruhe W. (2003) Radar bird observation and bird strike warnings in the

western Baltic region. �n: Proceedings of the 26th �nternational Bird

Strike Committee, Warsaw.

109References

Ryjov S. K. (2000) Outlook on development of means to repel birds.


Amsterdam.

Schaefer G. W. (1967) Bird Recognition by Radar: A study in Quantitative

Radar Ornithology. �n: The problems of birds as pests. (eds. R. K.

Murton & E. N. Wright). Academic Press, London/New York.

Seamans T. W. & Dolbeer R. A. (1999) Does tall grass reduce bird number

on airports?: Results of pen test with Canada geese and field trials

at two airports, 1998. �n: Proceedings of the 1st combined Bird Strike

committee USA/Canada, Richmond British Columbia, Canada.

Searing G. F. (2001) Counting bird strikes: Old science or new math? �n:

Proceedings of the joint meeting of Bird Strike Committee Canada and

Bird Strike Committee USA pp. 262, Calgary, Alberta.

Short J. J., Kelley M. E., Speelman R. J. & McCarty R. E. (2000) Birdstrike

prevention: Applying aero-science and bio-science. �n: Proceedings of

the 25th �nternational Bird Strike Committee, Amsterdam.

Sodhi N. S. (2002) Perspectives in Ornithology-Competition in the air:Birds

versus aircraft. The Auk 119: 587-595.

Solman V. E. F. (1969) Airport design and management to reduce bird

problems. �n: Proceedings of the World conference on bird hazards to

aircraft., Kingston, Ontario, Canada.

Solman V. E. F. (1978) Gulls and Aircraft. Environmental Conservation 5:

277-280.

110 References

Solman V. E. F. (1981) Birds and Aviation. Environmental Conservation 8:

45-52.

Stables E. R. & New N. D. (1967) Birds and Aircraft: the problems. In: The

problems of birds as pests (eds. R. K. Murton & E. N. Wright). Academic

Press, London/New York.

Stewart K. E. J., Bourn N. A. D. & Thomas J. A. (2001) An evaluation of

three quick methods commonly used to assess award height in ecology.

Journal of Applied Ecology. 38: 1148-1154.

Thorpe J. (2003) Fatalities and destroyed civil aircraft due to bird strikes,

1912-2002. �n: Proceedings of the 26th �nternational Bird Strike

Committee, Warsaw.

Tomlin A. D., Tolman J. H. & Thorn G. D. (1981) Suppression of earthworm

Lumbricus terrestris populations around an airport by soil application of

the fungicide Benomyl. Protection Ecology 2: 319-324.

Tomsons E. (1998) Falconry programme at Montreal airport contributes to

decline in bird strikes. �n: �nternational Civil Aviation Organisation (�CAO)

Journal pp. 7-8.

USGAO (2001) Report to Congressional Committees: Wildlife Services

Program; �nformation on Activities to Manage Wildlife Damage pp.

Publication no. GAO-02-138. United Stated General Accounting Office,

Washington D.C.

Van Tets G. F. (1969 A) Quantitative and qualitative changes in habitat and

avifauna at Sudney Airport. CS�RO Wildlife Research 14: 117-128.

111References

Van Tets G. F., Vestjens W. J. M. & Slater E. (1969 B) Orange runway lighting

as a mehtod for reducing bird strike damage to aircraft. CS�RO Wildlife

Research 14: 129-151.

Vickery J. A., Tallowin J. R., Feber R. E., Asteraki E. J., Atkinson P. W.,

Fuller R. J. & Brown V. K. (2001) The management of lowland neutral

grasslands in Britain: effects of agricultural practices on birds and their

food resources. Journal of Applied Ecology. 38: 647-664.

Weimerskirch H., Martin J., Clerquin Y., Alexandre P. & Jiraskova S. (2001)

Brief Communications: Energy Saving in Flight Formation. Nature 413:

697-698.

Weitz H. (2003) Rooks (Corvus frugilegus) at Giebelstadt US Army airfield

protecting the birds or reducing the birdstrike risk? �n: Proceedings of the

26th �nternational Bird Strike Committee, Warsaw.

Whittingham M. J. & Evans K. L. (2004) The effects of habitat structure on

predation risk of birds in agricultural landscapes. �bis 146: 210-220.

Whittingham M. J. & Markland H. M. (2002) The influence of substrate on

the functional response of an avian granivore and its implications for

farmland bird conservation. Oecologia 130: 637-644.

Wright E. N. (1967) Modification of the Habitat as a Means of Bird Control.

In: The problems of birds as pests. (eds. R. K. Murton & E. N. Wright).

Academic Press, London/New York.

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