Tuuli-Marjaana Koski

Department of Biology, University of Turku, Finland

Laaksonen T 1, Mäntylä E 1, Ruuskanen S 1, Li T 2, Girón-Calva P.S 2, Huttunen L 1 , Blande J.D 2 , Holopainen J.K 2 , Klemola T 1

1 Department of Biology, University of Turku, Finland2 Department Environmental Science of University of Eastern Finland, Finland

Volatile organic compounds: olfactory foraging cues for

insectivorous birds?

Introduction•Plant defences

►Direct►Indirect

• E.g. HIPVs=Herbivore-induced

plant volatiles Graph from: Arab A. & Bento J.M.S (2006) Plant Volatiles:

New Perspectives for Research in Brazil,

Neotropical Entomology 35(2):151-158.Plants are ”crying for help”

Introduction

• Insectivorous birds remove herbivores beneficial to plants

(e.g. Marquis & Whelan 1994; Mäntylä et al. 2011)

Introduction•Birds are attracted to insect-damaged trees (several studies)

►Without seeing the herbivores

►Without seeing the damages

Introduction•How birds detect insect-rich trees?

►Two obvious candidates• Vision

• Olfaction

Introduction

Olfactory cue hypothesis

► Do birds smell HIPVs?

• Some evidence support this

► Positive correlation between some HIPVs

and bird predation rate towards artificial prey

items (Mäntylä et al. 2008, 2014)

► Bird preference for chemical cues from

larval-damaged trees (Amo et al. 2013)

Do birds use HIPVs as olfactory foraging cues ?

•Experiments

1. VOC blends to artificial trees (aviary)

2. VOC blends to natural trees (field)

3. Larval-defoliated natural trees (aviary)

Experiment 1.

1. VOC blends to artificial

trees (aviary)

VOC blends mimicking herbivory

(terpenes)

VOC blends mimicking mechanical

damage (GLVs)

Aviary

Control (hexane)

VOC blends mimicking herbivory(terpenes)

Pied flycatcher(Ficedula hypoleuca)

N=20

First choice?

Bird photo: Markus Varesvuo, lintukuva.fi

Numb. of

visits?

Experiment 1. Results

0

2

4

6

8

10

12

Terpene VOC blend GLV VOC blend

Nu

mb

er

of b

irds

No difference in first choice

χ2 = 1.00, df = 1, P = 0.32

No difference in first choice

0

1

2

3

4

5

6

7

Terpene VOC blend Control

Nu

mb

er

of b

irds

Slight difference in the mean numbers of visits

Wilcoxon signed rank test: S = 35, P = 0.047

Two very active birds out of 20 tested

Wilcoxon signed rank test S = -10, P = 0.401

No difference in the mean numbers of visits

Experiment 2.

2. VOC blends to natural

trees (field)

•The same lab-made VOC blends as in Experiment 1.

► Two silicone tubes per tree• Trees again divided to either “herbivore-”,

“mechanical-” or control blend-treatments

► Four plasticine larvae per tree• Artificial prey for birds

Silicone tube

Plasticine larva

Photo by Elina Mäntylä

150 trees

Photos from: Mäntylä E, Alessio GA, Blande JD, Heijari J, et al. (2008) From Plants to Birds: Higher Avian Predation Rates in Trees Responding to Insect Herbivory. PLoS ONE 3(7):1-8.

Experiment 2.Results

No difference in probability of bird predation rate

F 2, 145 = 0.8 P = 0.45

Experiment 3.

3. Larval-defoliated natural

trees (aviary)

AviaryControlLarval-defoliated

30 30

Great tit, Parus major

First choice?

Blue tit, Cyanistes caeruleus

Numb. of

visits?

Bird photos: Markus Varesvuo, lintukuva.fi; planetscott.com

N = 123

• Larval-defoliated and control branches were removed before the experiment

• VOC measurements

Experiment 3.Results

0

5

10

15

20

25

30

35

40

Larval-defoliated Control

Nu

mb

er

of b

irds

No difference in first choiceχ2 = 1, df =1, P = 0.317

No difference in number of visits

F 1,119.6 = 0.48, P = 0.488   

•Significant difference in VOC emissions between larval- defoliation and control treatment among nine compounds

VOCs

* means p<0.05 and ** means p<0.01

Conclusions

•Attraction of insectivorous birds to herbivore-damaged trees has been shown several times

► One study suggest that HIPVs could act as olfactory foraging cues for insectivorous birds

(Amo, L. et al. 2013 ”Birds exploit herbivore-induced plant volatiles to locate herbivorous prey.” Ecology Letters, 16: 1348-1355.)

• Birds were not interested in HIPVs in our three experiments(apart from two individuals in comparison of number of visits between terpene- and GLV-trees)

► Olfactory cues may not be necessarily behind the attraction of birds to insect-defoliated trees

• Further studies are needed

► Olfactory foraging behaviour

► Use of vision during foraging

► Olfaction + vision

AcknowledgementsFunding

► Academy of Finland

► Emil Aaltonen Foundation

► Jenny & Antti Wihuri

Foundation

► UTUGS

► Finnish Cultural Foundation

► Oscar Öflund stiftelse

People

► Ruissalo and Kevo

field teams

► And all the other

people helping in

these experiments

Thank you for your attention!