Le régime alimentaire de la Chouette effraie, Tyto alba dans les Pyrénées-Orientales. Etude des variations écogéographiques

Abstract

Correspondence analysis is used to study the variations of the diet of the Barn Owl (Tyto alba) in the eastern part of the Pyrénées, and their relationship with the various vegetation zones of the area. Nineteen samples of owl pellets (18561 prey items) were collected, together with information on the altitude, climate, vegetation and land-use of the sites where pellets were gathered. In the eumediterranean zone, the Barn Owl preys mainly on Mus spretus, Pitymys pyrenaicus, Clethrionomys glareolus, Sorex «araneus» and S. minutus. Microtus arvalis is conspicuous by its absence. Mus spretus is a typical eumediterranean species. Pitymys pyrenaicus, Microtus arvalis, Clethrionomys glareolus, Sorex «araneus» and S. minutus are conspicuously absent. Pitymys duodecimcostatus, Suncus etruscus and Crocidura suaveolens cannot be considered as «indicator species» of the mediterranean biome. These small mammals take advantage of some man-made environmental changes to enter areas well outside the limits of the mediterranean bioclimate : e.g. cultivated fields with deep soils for Pitymys and dry-stone walls for Crocidurine shrews. The strong correlation existing between ecoclimatic factors and prey selection emphasizes the opportunistic nature of Barn Owl’s predatory behaviour. The use of fossil pellets as an indicator of past environmental conditions of a given area is amply justified.