BRUIJN O DE (1979) Feeding ecology of the Barn Owl Tyto alba in The Netherlands. LIMOSA 52 (3): 91-154.

Barn Owl Tyto alba This paper deals with the feeding ecology of the Barn Owl in the Netherlands. Following areview of the hunting techniques, territory size and food requirement (based mainly on a literature review) the prey selection of the Barn Owl in the Netherlands is discussed as follows. Since the pioneering research of Van den Brink (in the late 1920'ies) pellets have been collected all over the country; localities analysed in this paper are shown in figure I. In total more than 90.000 individual prey have been identified (table I). Small mammals account for 96% of the prey items, birds 3% and amphibians I% of the prey identified from the Barn Owl diet in the Netherlands (see table 2); these results are in close concordance with compilations from neighbouring regions (Uttendiirfer 1952). Because the factors computed by Southern (1954) for converting prey numbers into biomass are not in all cases applicable for the Dutch situation (Versluijs 1975), a new set of factors has been derived from weight data (table 3). - The majority of Barn Owls in the Netherlands rely on six small mammals as the staple food: the voles Microtus arvalis and Microtus agrestis, the shrews Sorex araneus and Crocidura russula, and the mice Apodemus sylvaticus and Mus musculus; in the South the vole Pitymys subterraneus joins the former species. Among birds (generally not more than 1-5% of the prey taken) the House Sparrow dominates. Although other prey species are important only on a local or temporary basis, they often provide important clues as to the hunting areas and hunting methods adopted by Barn Owls (discussed in section 5.2.2). Species boundaries of small mammals (voles, shrews, mice) tend to coincide with the boundaries of the districts recognized by plant geographers in the Netherlands (figure 2). If the small mammalfauna is classified according to the plant districts (table 4) it appears that the western and northern areas of holocene (= alluvial) origin have the most restricted mammalfauna (12 species) whereas the pleistocene (= diluvial) districts in the southern part of the nation attain 16-20 species. With reference to the plant districts (shown to be valid for the small mammalfauna as well) geografic variation of the Barn Owl diet within the Netherlands is analysed in table 5. In the

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