Transcript Kern - York College of Pennsylvania

Prey utilization by barn owls (Tyto alba)
Dustin Kern
Department of Biological Sciences, York College of Pennsylvania
prudentialhomesale.com
Introduction
Materials
Methods
• The barn owl (Tyto alba) is an iconic
farmland bird that has been associated
with humans and agriculture for centuries
(Bunn et al., 1982).
• The pellets were collected from 1 nest
box and 2 roost sites, in Dauphin
County, Pennsylvania, over the course
of nearly one year.
• Owl pellets have been utilized in many
studies to determine owl food habits, which
naturally contain small mammals,
particularly rodents (Pearson and Pearson,
1947).
• A dissection kit was used to break
apart casting pellets.
• Rodent infestations continue to cause
considerable property damage and
produce health risks in urban and rural
farmland (Albert et al., 2009).
• Anticoagulant rodenticides are frequently
used to control rodent pests (such as rats),
but poisoning of non-target wildlife has
been linked to such practices, including
secondary poisoning of birds of prey,
particularly owls (Newton et al., 1990).
• Rural applications of anticoagulant
rodenticides consumed by Barn Owls,
induce lethal hemorrhaging after feeding
on contaminated rats (Stone and
Okoniewski, 1999).
• This study utilizes pellet analysis,
derived from previous field experiments to
determine whether barn owls are catching
rats that could potentially be poisoned by
anticoagulant rodenticides.
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• A skull key was used to classify small
mammals found in pellets (DeBlase
and Martin, 1981).
Results
Table 2. Average weight and skull size of 5 rodent species caught by Barn Owls.
Weight (g)
35-60
15-30
15–23
16–30
140-280
• The entirety of the diet of Barn Owls
in this study consists of rodents.
• Analysis of regurgitated pellets
showed that meadow voles were the
most common prey at all sites and
dates.
• Although Rattus occurred in some
pellet collections, they made up only
a small part of the diet (2.1%) of Barn
Owls at all sites and dates.
Literature Cited
Table 1. Composition of prey (% and numbers) in the diet of Barn Owls in Dauphin County, PA.
M.H.S.
Ziegler’s
Halby’s
Ziegler’s Ziegler’s Ziegler’s
Total
Species Type
July
January
February
March
June
October
Species
2011
2012
2012
2012
2012
2012
(%)
Meadow Vole
79.4 (54)a
70.2 (33) 84.1 (37) 79.8 (83) 90.5 (67) 68.8 (66) 78.5 (340)
Short-tailed Shrew
8.8 (6)
12.8 (6)
9.1 (4)
8.7 (9)
5.4 (4) 11.5 (11) 9.2 (40)
House Mouse
10.3 (7)
4.3 (2)
6.8 (3)
3.8 (4)
1.4 (1)
7.2 (7)
7.0 (24)
White-footed Mouse
1.5 (1)
8.5 (4)
0 (0)
5.8 (6)
2.7 (2)
7.2 (7)
5.8 (20)
Rattus
0 (0)
4.3 (2)
0 (0)
1.9 (2)
0 (0)
5.2 (5)
2.1 (9)
Total
15.7 (68)
10.9 (47) 10.2 (44) 24.0 (104) 17.1 (74) 22.2 (96)
433
aNumber of specimens between parentheses.
Species Type
Meadow Vole
Short-tailed Shrew
House Mouse
White-footed Mouse
Rattus
Conclusions
Skull Length (mm)
25.8–28.8
20.8–24.8
20.4–22.5
24.1–27.4
42.0–47.0
• Albert, C. A., Wilson, L. K., Mineau, P.,
Trudeau, S., and Elliott, J. E. 2010.
Anticoagulant rodenticides in three owl
species from western Canada, 1988–2003.
Archives of environmental contamination and
toxicology, 58(2), 451-459.
• Bunn, D. S., Warburton, A. B., and Wilson R.
D. S. 1982. The Barn Owl. T. & A. D. Poyser:
Berkhamsted, England.
• DeBlase. A.F., and Martin, R.E. 1981. A
Manual of Mammalogy with Keys to Families
of the World. Wm. C. Brown Company
Publishers, Dubuque, IA.
• Newton, I., Wyllie, I., and Freestone, P. 1990.
Rodenticides in British barn owls.
Environmental pollution, 68(1), 101-117.
• Pearson, O. P., and A. K. Pearson. 1947. Owl
predation in Pennsylvania with notes on the
small mammals of Delaware County. J.
Mammal. 28: 137-147
Objective
• To determine if Barn Owls living near
humans, incorporate rats (a rodent
pest) in their diet.
Rattus
Meadow Vole
A regurgitated owl pellet.
Forceps used for dissection
Comparison of skulls
between 2 rodent species
• Stone, W. B., and Okoniewski, J. C. 1999.
Poisoning of wildlife with anticoagulant
rodenticides in New York. Journal of Wildlife
Diseases, 35(2), 187-193.
Acknowledgements
I would like to express thanks and appreciation to my Senior
Thesis Mentor, Dr. Karl Kleiner for his excellent guidance
during the completion of this research.