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THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 124. No. 3. September 2012 
Passenformes 
9 
50.5 
- 
12. 
\ 
i 
§- 0.0 
£ 
11 
*14 
• 
16 
Didelphlmorphia 
Columbiformes Anura 
Lagomorpha 
o Rodentia 
(native) 
-50.5 
Rodentia 
(exotic) 
-101.0 
1 
1 
-101.0 
-50.5 
0.0 
50.5 101.0 
PC 1(92.8%) 
FIG. 2. Representation of sites (black dots) and Western Barn Owl prey categories (open circles) on the plane defined 
by axes I and II ot a principal component analysis. Numbers for urban settlements correspond to those in Table 1. 
even in anthropically modified areas (e.g., Clark 
and Bunck 1991, Magrini and Facure 2008). 
However, we found high consumption rates of 
exotic rats and mice at the urbanized extreme of 
our gradient, demonstrating the opportunistic behav¬ 
ior of Bam Owls under certain environmental 
conditions (Taylor 2004). Commensal rodents arc 
mainly associated with human activities, and an 
increase in their abundance in Bam Ow l diets can be 
used as an indicator of environmental degradation 
(Clark and Bunck 1991). Moderate to high frequen¬ 
cies of exotic murid rodents were also repotted in the 
diet of this owl at other periurban localities of 
southern South America (e.g., Nores and Gutierrez 
1990. Gonzalez Acuna et al. 2004). 
The dominant prey species along the study 
gradient of the entire sample was Oligvryzomys 
flavescens, the main hantavirus reservoir in 
central-eastern Argentina (Enria and Levis 
2004). Hantaviruses are infectious agents dissem¬ 
inated by rodents in several parts of the world 
(Enria and Levis 2004); they cause Hantavirus 
Pulmonary Syndrome (HRS) with a lethality that 
reaches 50%, which is transmitted to humans 
through inhalation of particles in excretions of wild 
rodents. The expansion of urban areas is a reality in 
the present world (e.g., McKinney 2002) and 
political actions are needed to preserve minimum 
spaces o 1 natural habitats that ensure maintenance 
°f Predator-prey relationships. Barn Owls may 
have an important role in control of O. flavescens. 
especially at periurban places of central-eastern 
Argentina, where ~ 13 million people live and HPS 
is an endemic disease (Busch et al. 2004). 
ACKNOWLEDGMENTS 
Emiliano Muschetto and Martin Zamero participated in 
collection and disaggregation of owl pellets. U, F. J 
Pardinas provided some of the samples and literature, and 
made valuable comments on an earlier version of diis 
manuscript. 
LITERATURE CITED 
BELLOCQ, M. I. 1998. Prey selection by breeding and 
nonbreeding Bam Owls in Argentina. Auk 115:224—220 
Beuocq, M. I. 2000. A review of the trophic ecology of 
the Barn Owl in Argentina. Journal of Raptor Research 
34:108-119. 
BLAIR. R. B. 2001. Birds and butterflies along urban gradient* 
in two ecoregions of the U.S. Pages 33-36 in Biotic 
homogenization (J. L. Lockwood and M. L. McKinney- 
Editors). Kluwer, Norwcll. Massachusetts. I SA. 
B6. M. S.. A. V. BALADRON. and L. M. BlOMJl. 200’ 
Ecologia trdtica de Falconiformes y Strigifonw> 
tiempo de sintesLs. Homero 22:97-115. 
Brist. M AND F, GuidaLI. 2001. Seasonal and geographic 
differences in the diet of the Bam Owl in an agro- 
ecosystem in northern Italy. Journal of Raptor 
Research 35:240-246. 
Busch. M.. R. Cavia, a. E. Carbvjo. C. Bellomo. 5 
Gonzalez Capria, and P. Padula. 2004. Spatial and 
temporal analysis of the distribution of hantavirus 
pulmonary syndrome in Buenos Aires Province, ane 
its relation to rodent distribution, agricultural and 
demographic variables. Tropical Medicine and Inter¬ 
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