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RESEARCH ARTICLE
Contents Vol 31(1)

The effects of drought on prey selection of the barn owl (Tyto alba) in the Strzelecki Regional Reserve, north-eastern South Australia

Matthew C. McDowell A B and Graham C. Medlin A
+ Author Affiliations
- Author Affiliations

A Mammal Section, South Australian Museum, North Terrace, Adelaide, SA 5000, Australia.

B School of Biological Science, Flinders University of South Australia, PO Box 1200, Adelaide, SA 5000, Australia.

Australian Mammalogy 31(1) 47-55 https://doi.org/10.1071/AM08115
Submitted: 24 November 2008  Accepted: 21 March 2009   Published: 16 April 2009

Abstract

Changes in the diet of the barn owl (Tyto alba) were determined by analysing 619 egested pellets collected in eight samples over 12 months from a roost in the Strzelecki Regional Reserve, north-eastern South Australia. These data were used to examine the occurrence and change in frequency of small vertebrates in the region. In January 2003, at the end of a prolonged dry period, reptiles (predominantly geckos) dominated the diet of the barn owl, forming over 74% of Prey Units (PU%). This is the first Australian study to report reptiles as the primary prey of the barn owl. After substantial rain in February 2003, mammalian prey became much more common, and eventually accounted for almost 80 PU%. At least nine species of small mammal, at least four reptiles, nine birds and a frog were identified from the pellets. Mammalian prey included Leggadina forresti, Mus musculus, Notomys fuscus (endangered), Pseudomys desertor (not previously recorded in the reserve), P. hermannsburgensis, Planigale gilesi, Sminthopsis crassicaudata, S. macroura and Tadarida australis. This research showed that barn owls are capable of switching to alternative prey when mammals become rare, but that they return to preferred prey as soon as it becomes available.


Acknowledgements

This research was funded by Santos Ltd. We are very grateful to Steve Riley for his role in securing funding, and to Geoff Chennells (Santos Ltd), for collecting the owl pellets on which this research was based. We thank Catherine Kemper, David Stemmer, Mark Hutchinson, Philippa Horton and Maya Penck for access to their respective collections and aid in identifying specimens. We also thank the Bureau of Meteorology for providing the relevant rainfall data. We are grateful to Graham Carpenter, Catherine Kemper and Gavin Prideaux for providing comments on draft manuscripts. Finally, thanks go to the numerous volunteers – particularly Brian Ross, Zbigniew Rudnicki and Terry Kennedy – who helped to process and dissect over 600 barn owl pellets. The quality of the paper was further enhanced by the constructive comments of three anonymous referees.


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Appendix 1.  Prey Unit values for Merty Merty taxa
Mammal weights are after Strahan (1995). Bird weights are after Higgins (1999), Marchant et al. (1994), Higgins et al. (2001), Higgins and Peter (2003) and rHiggins et al. (2006). Reptile and amphibian weights were estimated according to body size. ( ) = average
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