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Weather-dependent variation in the winter diet of urban roosting Long-eared Owls (Asio otus) in Pécs (Hungary)

Posted on 7. February, 2018.

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Long-eared Owls (Asio otus)  usually winter in groups in settlements, hunt at night and rest in evergreen trees during the day. From prey remnants regurgitated as pellets, one can detect species present in their hunting areas and changes in their abundance. Our aim was to reveal how the ratio of small mammal species in Long-eared Owl prey changes during the winter, since weather can influence hunting success and the availability of prey.

There were 40–60 Long-eared Owls wintering in the city of Pécs. From November 2014 to mid-March 2015 we collected 6,328 pellets from which 9,087 prey remains were identified. 97.5% of prey consisted of small mammals belonging to 21 species. The diversity of small mammals in the pellets collected in November was significantly lower in comparison with other months. With the increase of precipitation, the relative abundance of the Common Vole (Microtus arvalis) and Common Dormouse (Muscardinus avellanarius) decreased, while that of the Striped Field Mouse (Apodemus agrarius) and Wood Mouse (A. sylvaticus) increased. In the periods when the area was covered by snow, the ratio of the Common Vole as prey continually decreased, probably because it stayed under the snow. Since the availability of the Common Vole declined, the proportions of the Striped Field Mouse and Lesser White-toothed Shrew (Crocidura suaveolens) as alternative prey grew significantly. In low temperature periods, Brown Rats (Rattus norvegicus) and birds are more often preyed upon. Despite the hunting area being predominantly urban, species preferring open grassland habitats were significantly more common. As winter progressed, the role of forest-dwelling species in the diet continuously increased.

Read the full article in Avian Biology Research, Volume 11, Number 1, February 2018, pp. 1-6

Authors: Dávid Szép, Renáta Bocz and JenÅ‘ J. Purger*
Department of Ecology, Institute of Biology, University of Pécs, Ifjúság Útja 6, 7624 Pécs, Hungary

Keywords: diversity, habitat preference, pellet analysis, precipitation, small mammals