SELECTIVE USE OF NEST LINING MATERIALS BY BURROWING OWLS

1

• 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 its 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.

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.

RESULTS
Figs 45. 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.

• 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.

Manure Proportion
Manure Weight
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
Historys Frank Chapman Memorial Research Fund.
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,
91347-354.   Griebel, R.L. 2000. Ecological
and physiological factors affecting nesting
success of burrowing owls in Buffalo Gap
National Grassland. Masters 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, 75446-456.   Thomsen, L. 1971. Behavior
and ecology of burrowing owls on the Oakland
municipal airport. Condor, 73177-192.   Vellenga,
R. 1970. Behaviour of the male satin bowerbird
at the bower. Austral. Bird Bander,
13-11.   Yosef, R. 1999. Function of stone
carpets at the nest entrance of blackstarts
Cercomela melanura. Vogelwelt,
120(3) 155-161.
Figs 12. 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.