SELECTIVE USE OF NEST LINING MATERIALS BY BURROWING OWLS
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SELECTIVE USE OF NEST LINING MATERIALS BY BURROWING OWLS Matthew Denman Smith and Courtney J. Conway Arizona Cooperative Fish and Wildlife Research Unit, The University of Arizona, Tucson, AZ DO BURROWING OWLS SELECTIVELY CHOOSE MANURE TO LINE THEIR NEST BURROWS? INTRODUCTION • Burrowing owls, Athene cunicularia, often collect and line the entrance and tunnel leading down to their nest chamber with dried mammal manure (Bendire 1892), shredded carpet, paper, plastic, cotton, golf course divots, tin foil, and / or other mateials (Thomsen 1971, pers. observ.). • The adaptive function of foreign objects brought to the nest is not well known in burrowing owls. • Despite the presence of other materials, hypotheses to explain the nest-lining behavior have exclusively focused on the use of manure. • Possible hypotheses to explain the function of nest-lining behavior include: olfactory camouflage from predators (Martin 1971, Green and Anthony 1989), insulation (Martin 1971), absorption of water for flood protection (Greibel 2000), and reduction of carbon dioxide levels (Brady and Beltoff, pers. comm.). An alternative hypothesis that has not previously been tested is the attraction of insect prey. • Some hypotheses predict that owls should preferentially choose manure to line their nest burrow, whereas other hypotheses adequately explain the use of materials other than manure. Hence, understanding the degree to which owls actively choose manure over other possible nest-lining materials may help discriminate among possible adaptive explanations of this odd behavior. • The urban, industrial, agricultural and ranching communities of south-central WA provide a unique opportunity to study the selection of nest-lining materials, because manure is readily available in some areas where burrowing owls nest, but not in others. METHODS Supply Stations • At each of 12 randomly-selected nest burrows we supplied 2 liters of 4 types of materials often found at burrowing owl nests: carpet pieces (260 g), grass divots from golf courses (330 g), dried manure (510 g), and tin foil (70 g). • We placed the materials at a random azimuth, 10 meters away from each nest burrow. Material Collection • At 21 randomly-chosen nest burrows we collected, dried, and weighed all foreign material found on the burrow mound and within the first meter of the nest tunnel. • We measured the distance to the nearest source of manure at each of the 21 nest burrows. REFERENCES Bendire , C.E. 1892, in: Bent A.C. 1938. Life Histories of North American Birds. U.S. Nat. Mus. Spec. Bull.1. Green, G.A. and R.G. Anthony. 1989. Nesting success and habitat relationships of burrowing owls in the Columbia basin, Oregon. Condor, 91:347-354. Griebel, R.L. 2000. Ecological and physiological factors affecting nesting success of burrowing owls in Buffalo Gap National Grassland. Master’s Thesis. University of Nebraska. Marshall, A.J. 1954. Bower-Birds: Their Displays and Breeding Cycles. Oxford: Clarendon Press. Martin, D.J. 1973. Selected aspects of burrowing owl ecology and behavior. Condor, 75:446-456. Thomsen, L. 1971. Behavior and ecology of burrowing owls on the Oakland municipal airport. Condor, 73:177-192. Vellenga, R. 1970. Behaviour of the male satin bowerbird at the bower. Austral. Bird Bander, 1:3-11. D istance (m )to the nearestsource ofm anure 0 200 400 600 800 1000 1200 M anure proportion ofnestlining m aterial 0 20 40 60 80 100 n = 21 R 2 = .75 p = .0001 D istance (m )to N earestSource ofM anure 0 200 400 600 800 1000 1200 W eight(g)ofM anure Found in N estLining -50 0 50 100 150 200 250 300 n = 21 p = .003 N estLining M aterial M anur e G rass Org.Clum ps C anine Scat D ecorations Shred.Paper O therScat Average Proportion 0 10 20 30 40 50 G rass > M anure,p = .053 M aterial M anure Divots C arpet Tin Foil Average W eight(g)ofM aterial U sed 0 100 200 300 400 500 M aterial M anure G rass D ivots C arpet Tin Foil % ofSupplied U sed by O wls 0 10 20 30 40 50 60 70 DISCUSSION • Negative relationships between the distance to the nearest source of manure and both the weight and proportion of manure, suggests that owls use manure in proportion to it’s convenience and availability in the landscape. • The frequent use of grass to line nest burrows, and the selective use of grass divots during our selection experiments, suggests that the use of grass to line nest burrows also serves some adaptive function. • Hypotheses to explain the adaptive function for use of manure to line nest burrows should also explain the preferential use of grass. • We are currently testing 3 adaptive hypotheses to explain nest-lining behavior: olfactory camouflage, prey attraction, and burrow ownership. RESULTS ACKNOWLEDGEMENTS Thanks to our field workers: C. Forristal, D. Hearne, M. Hearne, T. McLaughlin, S. Millus, P. Ramey, C. Sanders, and A. Sanfacon. Special thanks to Sandpiper Technologies and the American Museum of Natural History’s Frank Chapman Memorial Research Fund. Figs 1&2. Proportion of manure in nest-lining material decreases as the distance from a source of manure increases. Fig 3. Grass and manure are the most common nest- lining materials used. Manure Proportion Manure Weight Figs 4&5. Owls preferred manure and grass divots and avoided carpet and tin foil as nest-lining material in our supply-station selection trials. We detected no difference between the amount of manure and grass divots selected.
description
DISCUSSION Negative relationships between the distance to the nearest source of manure and both the weight and proportion of manure, suggests that owls use manure in proportion to it’s convenience and availability in the landscape. - PowerPoint PPT Presentation
Transcript of SELECTIVE USE OF NEST LINING MATERIALS BY BURROWING OWLS
SELECTIVE USE OF NEST LINING MATERIALS BY BURROWING OWLS
Matthew Denman Smith and Courtney J. ConwayArizona Cooperative Fish and Wildlife Research Unit, The University of Arizona,
Tucson, AZ
DO BURROWING OWLS SELECTIVELY CHOOSE MANURE TO LINE THEIR NEST BURROWS?
INTRODUCTION • Burrowing owls, Athene cunicularia, often collect and line the entrance and tunnel
leading down to their nest chamber with dried mammal manure (Bendire 1892), shredded carpet, paper, plastic, cotton, golf course divots, tin foil, and / or other mateials (Thomsen 1971, pers. observ.).
• The adaptive function of foreign objects brought to the nest is not well known in burrowing owls.
• Despite the presence of other materials, hypotheses to explain the nest-lining behavior have exclusively focused on the use of manure.
• Possible hypotheses to explain the function of nest-lining behavior include: olfactory camouflage from predators (Martin 1971, Green and Anthony 1989), insulation (Martin 1971), absorption of water for flood protection (Greibel 2000), and reduction of carbon dioxide levels (Brady and Beltoff, pers. comm.). An alternative hypothesis that has not previously been tested is the attraction of insect prey.
• Some hypotheses predict that owls should preferentially choose manure to line their nest burrow, whereas other hypotheses adequately explain the use of materials other than manure. Hence, understanding the degree to which owls actively choose manure over other possible nest-lining materials may help discriminate among possible adaptive explanations of this odd behavior.
• The urban, industrial, agricultural and ranching communities of south-central WA provide a unique opportunity to study the selection of nest-lining materials, because manure is readily available in some areas where burrowing owls nest, but not in others.
METHODS
Supply Stations
• At each of 12 randomly-selected nest burrows we supplied 2 liters of 4 types of materials often found at burrowing owl nests: carpet pieces (260 g), grass divots from golf courses (330 g), dried manure (510 g), and tin foil (70 g).
• We placed the materials at a random azimuth, 10 meters away from each nest burrow.
Material Collection
• At 21 randomly-chosen nest burrows we collected, dried, and weighed all foreign material found on the burrow mound and within the first meter of the nest tunnel.
• We measured the distance to the nearest source of manure at each of the 21 nest
burrows.
REFERENCES
Bendire, C.E. 1892, in: Bent A.C. 1938. Life Histories of North American Birds. U.S. Nat. Mus. Spec. Bull.1.
Green, G.A. and R.G. Anthony. 1989. Nesting success and habitat relationships of burrowing owls in the Columbia basin, Oregon. Condor, 91:347-354. Griebel, R.L. 2000. Ecological and physiological factors affecting nesting success of burrowing owls in Buffalo Gap National Grassland. Master’s Thesis. University of Nebraska. Marshall, A.J. 1954. Bower-Birds: Their Displays and Breeding Cycles. Oxford: Clarendon Press. Martin, D.J. 1973. Selected aspects of burrowing owl ecology and behavior. Condor, 75:446-456. Thomsen, L. 1971. Behavior and ecology of burrowing owls on the Oakland municipal airport. Condor, 73:177-192. Vellenga, R. 1970. Behaviour of the male satin bowerbird at the bower. Austral. Bird Bander, 1:3-11. Yosef, R. 1999. Function of stone carpets at the nest entrance of blackstarts Cercomela melanura. Vogelwelt, 120(3): 155-161.
Distance (m) to the nearest source of manure
0 200 400 600 800 1000 1200
Ma
nu
re p
rop
ort
ion
of n
est
linin
g m
ate
ria
l
0
20
40
60
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100
n = 21R2 = .75p = .0001
Distance (m) to Nearest Source of Manure
0 200 400 600 800 1000 1200
We
igh
t (g
) o
f Ma
nu
re F
ou
nd
in N
est
Lin
ing
-50
0
50
100
150
200
250
300
n = 21p = .003
Nest Lining Material
ManureGrass
Org. Clumps
Canine Scat
Decorations
Shred. Paper
Other Scat
Ave
rage
Pro
por
tion
0
10
20
30
40
50
Grass > Manure, p = .053
Material
Manure Divots Carpet Tin Foil
Ave
rage
We
ight
(g)
of M
ate
rial
Use
d
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500
Material
Manure Grass Divots Carpet Tin Foil
% o
f Sup
plie
d U
sed
by
Ow
ls
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10
20
30
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50
60
70
DISCUSSION • Negative relationships between the distance to the nearest source of
manure and both the weight and proportion of manure, suggests that owls use manure in proportion to it’s convenience and availability in the landscape.
• The frequent use of grass to line nest burrows, and the selective use of grass divots during our selection experiments, suggests that the use of grass to line nest burrows also serves some adaptive function.
• Hypotheses to explain the adaptive function for use of manure to line nest burrows should also explain the preferential use of grass.
• We are currently testing 3 adaptive hypotheses to explain nest-lining behavior: olfactory camouflage, prey attraction, and burrow ownership.
RESULTS
ACKNOWLEDGEMENTS Thanks to our field workers: C. Forristal, D. Hearne, M. Hearne, T. McLaughlin, S. Millus, P. Ramey, C. Sanders, and A. Sanfacon. Special thanks to Sandpiper Technologies and the American Museum of Natural History’s Frank Chapman Memorial Research Fund.
Figs 1&2. Proportion of manure in nest-lining material decreases as the distance from a source of manure increases.
Fig 3. Grass and manure are the most common nest- lining materials used.
Manure Proportion Manure Weight
Figs 4&5. Owls preferred manure and grass divots and avoided carpet and tin foil as nest-lining material in our supply-station selection trials. We detected no difference between the amount of manure and grass
divots selected.
