Conservation assessment of the nominate subspecies of Eurasian Oystercatchers
Transcript of Conservation assessment of the nominate subspecies of Eurasian Oystercatchers
1
Norwegian University of Science and TechnologyCentre for Conservation Biology
Conservation assessment of the nominate subspecies of Eurasian Oystercatchers
(Haematopus ostralegus ostralegus)
Martijn van de Pol
Phil Atkinson, Jan Blew, Olivia Crowe, Simon Delany, Olivier Duriez, Bruno Ens, Bernd Hälterlein, Hermann Hötker, Karsten Laursen, Kees
Oosterbeek, Aevar Petersen, Ole Thorup, Kathleen Tjørve, Patrick Triplet
2
Norwegian University of Science and TechnologyCentre for Conservation Biology
Taxonomic status (Hockey 1996; Sibly & Monroe 1990)
Haematopus ostralegus ostralegus is the nominate subspecies of Eurasian Oystercatchers
Other subspecies are
H.o. longipes (Eastern Eurasia)
H.o. osculans (East Asia)
H.o. finschi (New Zealand) [often regarded as separate species]
Sometimes also
H.o. malacophaga (Iceland and Faeroe)
H.o. occidentalis (United Kingdom and Ireland)
Here these two are grouped within H.o. ostralegus
3
Norwegian University of Science and TechnologyCentre for Conservation Biology
Life history
Medium sized, sexually monomorphic, pied Oystercatcher
Long term socially monogamous pair bonds
Polygyny (~1%)
EPY (~2%)
Highly territorial (nesting and feeding territory)
Extreme site-fidelity to breeding sites
Site-fidelity to wintering sites
Bi-parental care, equal shares
4
Norwegian University of Science and TechnologyCentre for Conservation Biology
Life cycle
Timing of breeding varies strongly geographically
Single brooded with replacement clutches
Incubation 28 days, fledging 35 days
Semi-precocial and extended parental care (several months)
First two years low site fidelity
Sexually mature age 3 (adult plumage)
Delayed reproduction due to habitat saturation
Usually limited natal and breeding dispersal (<10km)
5
Norwegian University of Science and TechnologyCentre for Conservation Biology
range: 3-16 years
Age of first reproduction (years)
6
Norwegian University of Science and TechnologyCentre for Conservation Biology
Life cycle
One of the longest living waders (record 43 yrs)
Generation time 11 years (IUCN), but probably higher
1st year survival ~0.5 [from day 30]
2nd year survival ~0.8
3rd year/adult survival ~0.9
Adult survival can drop to 0.7 in occasional years (cold and/or low food)
Reproduction ~0.3 with many years with almost no young intermixed with occasional good years
No known latitudinal gradients in vital rates (birds in north larger)
7
Norwegian University of Science and TechnologyCentre for Conservation Biology
Environmental stochasticity
Atkinson et al. 2003
(Wash, UK)1984 1988 1992 1996 2000 2004
Van de Pol et al. 2006
(Schiermonnikoog, NL)
Fledglings / nestFled
glin
gs /
pair
Need many years of data…
Oosterbeek
et al. 2006
8
Norwegian University of Science and TechnologyCentre for Conservation Biology
Feeding ecology Large prey spectrum
Mussels & cockles staple food
In summer Baltic tellin, ragwormand lugworm more prominent
Locally other bivalve, gastropod and crustacean species important
In agricultural fields leatherjackets and earthworms eaten
Most individuals specialize:
9
Norwegian University of Science and TechnologyCentre for Conservation Biology
Habitat & migrationBreeding habitat
Mainly coastal areas (salt marsh, beaches, dunes)
In 20th century more inland (arable land, grassland, roofs)
Productivity salt marsh > agricultural lands > dunes ?
Overwintering habitat
Estuaries near the coast
Agricultural lands sometimes also used
Some populations resident, many migratory.
Long-distant migrant
In cold years or low food stocks → mass migration
→ atypical winter distribution
10
Norwegian University of Science and TechnologyCentre for Conservation Biology
H.o. longipes
BreedingWinterBreeding & winterBarrier for natal and breeding dispersal?
Demarcation ostralegusand longipes subspecies
Distribution and (sub)populations
Atlantic
Continental
?
H.o
. ost
rale
gus
Iceland 4%
Faeroe 3%
UK & Ireland 31%
Nordic 18%
Low countries 43%
11
Norwegian University of Science and TechnologyCentre for Conservation Biology
ContinentalAtlanticAtlant. & Contin.
16 key sites
Max. counts
(O. Duriez, unpublished data)
Official 1% threshold
is 10,200 individuals
Winter migration and distribution
Migration routeRare migr. route
12
Norwegian University of Science and TechnologyCentre for Conservation Biology
Stroud et al. 2004:
1,020,000 (1990s)
Thorup 2006:
309,000-424,000 pairs
13
Norwegian University of Science and TechnologyCentre for Conservation Biology
United KingdomNetherlandsNorwayGermanyIceland
United KingdomGermanyNetherlandsIreland
31%
30%
11%
9%
4%
4%
3%3%
2%1% 2%
SwedenDenmarkFaeroe IslandsRussia FinlandOther
37%
21%
21%
8%
6%
3% 3% 1%
FranceDenmarkAfricaOther
Summer Winter
UK UK
GE
NL
IR
FRDK
NLNO
GE
ICSW
DKFA
AFR
+ most data available
+ most reliable data- less data available
- less reliable data
14
Norwegian University of Science and TechnologyCentre for Conservation Biology
Year
1975 1980 1985 1990 1995 2000 2005
Year
1975 1980 1985 1990 1995 2000 20050
25
50
75
100
125
150
0
25
50
75
100
125
150
Germany Denmark(Wadden Sea area only)
United Kingdom(including Northern Ireland)
NetherlandsB
reed
ing
Inde
xsummer 1996=100
No data for Norway (11%), Iceland (4%), Sweden (4%), Faeroe (3%), Russia (2%), Finland (1%)
15
Norwegian University of Science and TechnologyCentre for Conservation Biology
Year
1975 1980 1985 1990 1995 2000 2005
Year
1975 1980 1985 1990 1995 2000 20050
25
50
75
100
125
150
175
0
25
50
75
100
125
150
175
0
25
50
75
100
125
150
175
France Denmark(Wadden Sea area only)
Germany(Wadden Sea area only)
Netherlands
United Kingdom(Northern Ireland excluded)
Ireland(Northern Ireland included)
Win
ter I
ndex
Winter
2001 =100
16
Norwegian University of Science and TechnologyCentre for Conservation Biology
NetherlandsGermany
Denmark
0
100,000
200,000
300,000
400,000
500,000
1986 1988 1990 1992 1994 1996 1998 2000 2002 2004Year
Num
bers
Wadden Sea (Blew et al. 2007)To
tal w
inte
r num
bers
17
Norwegian University of Science and TechnologyCentre for Conservation Biology
2000s1990s1980s1970s
Bre
edin
g pa
irs
(x 1
000)
Win
terin
g bi
rds
(x 1
000)
252
100
200
300
400
500
367
Goss-Custard et al. 1995; Hulscher 1997
365
Thorup 2006 This assessment
Goss-Custard et al. 1996
200
400
600
800
1000
874
Rose & Scott 1997
1,020
816
Stroud et al. 2004 This assessment
Goss-Custard et al. 1996
18
Norwegian University of Science and TechnologyCentre for Conservation Biology
Bre
edin
g pa
irs
(x 1
000)
Win
terin
g bi
rds
(x 1
000)
252
100
200
300
400
500
367
Goss-Custard et al. 1995; Hulscher 1997
365
Thorup 2006 This assessment
Goss-Custard et al. 1996
200
400
600
800
1000
874
Rose & Scott 1997
1,020
816
Stroud et al. 2004 This assessment
Goss-Custard et al. 1996
2000s1990s1980s1970s
19
Norwegian University of Science and TechnologyCentre for Conservation Biology
Protection statusIUCN
>30% observed (or projected) decrease in:
10 years or 3 generations (=33 years)
whichever period is longer
“Least concern”(IUCN categorizes the whole H. ostralegus
species)
1. H.o. ostralegus(816,000)
2. H.o. longipes(100,000-200,000)
3. H.o. osculans(10,000)
IUCN should categorize per subspecies!
20
Norwegian University of Science and TechnologyCentre for Conservation Biology
Year
1975 1980 1985 1990 1995 2000 2005
Year
1975 1980 1985 1990 1995 2000 20050
25
50
75
100
125
150
175
0
25
50
75
100
125
150
175
0
25
50
75
100
125
150
175
France Denmark(Wadden Sea area only)
Germany(Wadden Sea area only)
Netherlands
United Kingdom(Northern Ireland excluded)
Ireland(Northern Ireland included)
Win
ter I
ndex
33 years
33 years
21
Norwegian University of Science and TechnologyCentre for Conservation Biology
Demographic and mechanistic causes
of population change
What has caused the strong (initial) increase over most of the 20th century?
Successful adaptation breeding inland?
More moist agricultural lands became available
Agricultural lands became more fertilized
22
Norwegian University of Science and TechnologyCentre for Conservation Biology
Demographic and mechanistic causes
of population change
What has caused the strong (initial) increase over most of the 20th century?
Successful adaptation breeding inland?
However numbers also increased in coastal areas (Goss-Custard et al. 1996)
24
Norwegian University of Science and TechnologyCentre for Conservation Biology
Demographic and mechanistic causes of population change
What has caused the strong (initial) increase over most of the 20th
century?
Successful adaptation breeding inland?
However numbers also increased in coastal areas
Hatching success high in 1930-60s and later decreased.
Successful adaptation, high productivity in coastal areas (source-sink dynamics) or both?
25
Norwegian University of Science and TechnologyCentre for Conservation Biology
Demographic and mechanistic causesMore recent decline in Netherlands:
Primarily caused by over-exploitation due to mechanical shell-fisheries (mussels and cockles).
Reduces (juv & ad) survival, primarily in cold winters (Atkinson et al. 2003; Ens et al. 2004)
Reduces reproductive output (low food stocks and body condition at start of breeding) (Van de Pol et al. 2006; Oosterbeek in prep.)
Shell-fisheries disturbs the soil and changes benthic fauna (Piersma et al. 2001)
Additional role reduced eutrophication
Reduces nutrients for shell-fish stocks (Phillipart et al. 2007; Ens 2006)
Additional role agricultural intensification
Frequent mowing reduces reproduction (Hulscher & Verhulst 2001)
Demographic cause: reproduction > survival?
26
Norwegian University of Science and TechnologyCentre for Conservation Biology
Demographic and mechanistic causes of population change
More recent decline Germany and Denmark:
Causes not well understood → need more research
Increase France:
Thought to have resulted from birds choosing to overwinter in France instead of Wadden Sea (Triplet and Maheo 2000)
Decline Norway(?):
Halving of number of (Norwegian) Oystercatchers migrating through Denmark form 1990s to 2000s (Meltofte et al. 2006)
Meltofte (2006) suggests that Norwegian population has decreased, but no recent surveys available and expert opinions disagree
Alternatively, Norwegian birds now overwinter in UK more often
27
Norwegian University of Science and TechnologyCentre for Conservation Biology
Threats (1)
Mechanical shell-fisheries (major threat) :
As discussed before
In UK also affected survival in mild years and does not result in mass migration
Aberrant moult patterns
Reductions in carrying capacity of estuaries can be large (e.g.estimated decrease of 30% due to cockle fisheries in Westerschelde)
(Rappoldt & Ens 2006)
Hand shell-fisheries:
Less detrimental as long as scale is limited(Atkinson et al. 2006; Stillman et al. 2001)
But effects on spring numbers have been reported (Norris et al. 1998)
28
Norwegian University of Science and TechnologyCentre for Conservation Biology
Threats (2)
Bait-digging
Strong local reduction in worm prey (Lambeck et al. 2006)
Can increase cockle mortality (Jackson & James 1979)
Mechanical bait-digging disturbs the soil (Lambeck et al. 2006)
Agricultural intensification
Some fertilization good, too much fertilization and pesticides is detrimental for earthworms (Duriez et al. 2005)
Frequent mowing reduces egg and chick survival
High cattle densities causes trampling of nests (Beintema & Muskens 1987)
29
Norwegian University of Science and TechnologyCentre for Conservation Biology
Threats (3)Eutrophication
Decreased eutrophication reduces shellfish productivity(Phillipart et al. 2007; Brinkman & Smaal 2004)
In turn, declining shellfish stocks have caused fishermen to overexploit the littoral mussel beds (Ens 2006)
Habitat loss
Last 300 years much habitat loss due to humans (Lambeck et al 1996)
National and EU legislation make habitat loss less ikely in the future
Even opportunities for habitat restoration (Eertman et al. 2002)
However sea level rise is resulting in increased erosion in UK (2-7% per year), but not in the Wadden Sea (Norris et al. 2004; Wolters et al. 2005)
30
Norwegian University of Science and TechnologyCentre for Conservation Biology
Threats (4)Climate change
Laying date has advanced with 8 days from 1965-2005 (BTO website)
Prey species sensitive to temperature (negative impact)
Cold winters that cause mass mortality are expected to be less common (positive impact)
Hunting
Most countries legally protected since 1980s or not hunted
However, in France substantial numbers are shot each year (1,800-2,000), especially in cold winters (8,000-17,000) (Trolliet 2000; Triplet 2000)
This may represent a major source of mortality and may have population consequences that have not yet been quantified
31
Norwegian University of Science and TechnologyCentre for Conservation Biology
Threats (5)Human disturbance
Many types of anthropogenic disturbance (recreation, military, agriculture)
The effect of anthropogenic disturbance depends on the specific source, but are typically stronger than natural disturbances (Kirby et al. 1993)
Recreation is increasing
Could make areas previously suitable for roosting, feeding or breeding no longer profitable, but quantitative consequences hard to estimate
Parasites and diseases
Major unknown
No avian influenza (Munster et al. 2007)
Gut-parasites common (helminths); effects on vital rates unknown (Norris 1999; van Oers et al. 2002)
32
Norwegian University of Science and TechnologyCentre for Conservation Biology
Threats (6)Predators and competitors
Suggested foxes played role in decrease breeding numbers (Willems et al. 2005)
Pacific oyster (Crassostrea gigas) is non-native invasive species
Increasing strongly in numbers
Not eaten by Oystercatchers or other predators
Taking over mussel beds
Compete for same resources and may also eat larvae of cockles and mussels
However, might also facilitate re-establishment of new mussel beds(Cadée 2007)
33
Norwegian University of Science and TechnologyCentre for Conservation Biology
Recommendations for research (1)1. Improve surveys
We lack good surveys for the sparsely populated and large breeding areas in all Nordic countries, especially Norway (10% of world population and possibly declining)
2. Meta-population structure (breeding and winter movements)
Start long-term color-ringing and monitoring programs in main breeding area (UK, Norway, Germany, Denmark, Faeroe, Iceland)
Stronger focus on role inland breeding sites (source-sink dynamics)
Start winter color-ringing programs for main winter areas (Dutch delta, Germany, Ireland, France, Denmark);
Satellite track small groups of individuals
Include ringing data in EUring database, not very useful now
Analyze genetic structure of potential (sub)populations(van Treuren et al. 1999)
34
Norwegian University of Science and TechnologyCentre for Conservation Biology
Recommendations for research (2)
3. Mechanistic causes decline Germany & Denmark
Stimulate color-ringing studies
Relate egg and chick survival to food availability
Relate local trends in winter numbers to habitat and food quality.
4. Demographic causes of population change
Most population models either focus on how winter-conditions affect survival or how summer conditions affect reproduction.
Awareness is growing that there can be important feedback between overwinter conditions and reproductive output
Such feedbacks advocates for demographic models that include both the summer and winter stage.
35
Norwegian University of Science and TechnologyCentre for Conservation Biology
Recommendations for research (3)
5. Climate change
Existing models should be used to quantify the effects of sea level rise and habitat loss.
(Goss-Custard et al. 1995; Sutherland 1996; Rappoldt et al. 2004)
6. Recreation
Determine exact influence of human disturbance on breeding and non-breeding Oystercatchers
Determine the potential for habituation to specific types of disturbances
Preserve some areas without disturbance (e.g. in nature reserves) as reference area
36
Norwegian University of Science and TechnologyCentre for Conservation Biology
Recommendations for research (4)
7. Skewed sex-ratios and effective population sizes
Suggested many winter-populations are strongly male-biased(Durell & Atkinson 2004; Durell 2006)
This means that effective population sizes are much smaller thanpreviously reported
However, estimates based on biometric sex-discrimination, which might be unreliable (van de Pol et al, submitted)
Mechanism of sex-ratio bias is unknown
Therefore, we need large scale DNA sampling of fledglings in breeding areas and adults at roosts
37
Norwegian University of Science and TechnologyCentre for Conservation Biology
Recommendations for management1. Mechanical shell-fisheries
Creation of small marine protected areas where shellfisheries are excluded does not seem to result in a redistribution of birds, and thus
are not a solution to the problem of mechanical shell-fisheries. (Verhulst et al. 2004)
2. Hunting
In cold winters Oystercatchers mass migrate to France from more northerly estuaries. Currently hunting is usually forbidden after several days of continuing frost, when large numbers of birds have already been shot.
International agreements should be made to temporarily stop hunting as soon as a cold spell is detected in northern Europe. This interdiction should last 1-2 weeks to let birds recover body conditions to return to their usual wintering grounds.
38
Norwegian University of Science and TechnologyCentre for Conservation Biology
Summary conservation statusMost abundant and best studied Oystercatcher (sub)species
Numbers have increased over most 20th century but have recently dropped with 200,000
Decline in Netherlands mainly caused by shell-fisheries, but this is now strongly restricted and numbers are expected to increase again
Cause of decline in Germany and Denmark not known, future less clear
Good data for Nordic countries (especially Norway) much needed
Overall status still of ‘Least Concern’
39
Norwegian University of Science and TechnologyCentre for Conservation Biology
AcknowledgmentsSupported by Rubicon fellowship of the Netherlands Organization for Scientific Research (NWO)Centre for Conservation Biology, NTNU TrondheimDorete Bloch, Hans Meltofte, John Atle Kålås, Svein-Håkon Lorentsen, Even Tjørve, Ingar Øien and the people at the Norsk Ornithologisk Forening for help
PDF of presentation & conservation assessment at www.MyScience.eu/Oystercatcher