Comparison of methods for diet analysis and prey preference: a case study on the Red-backed Shrike Lanius collurio

I studied diet composition and prey preferences of the Red-backed Shrike (Lanius collurio) in an extensive agricultural landscape in the eastern part of Poland. The diet composition of the Red-backed Shrike was described based on the analysis of animal remains in pellets (n = 968 prey items), larders (n = 115), butchering points (n = 1180) and nests (n = 79). Remains from all methods combined showed that Insecta predominated in the diet, comprising 98.9% of all prey items. Coleoptera prevailed decidedly (83.6%), followed by Hymenoptera (8.0%), Orthoptera (3.8%), Heteroptera (1.5%) and Diptera (1.1%). The proportions of the taxa in the diet of the Red-backed Shrike differed between the methods of food analysis, mainly with respect to Hymenopterans and Orthopterans. I found differences in the proportion of taxa between nests and butchering points, nests and larders and between animal remains in pellets and larders. I studied preference by comparing the proportions of potential prey of the Red-backed Shrike with the proportion of these prey items in their food. Red-backed Shrikes prefer beetles and Hymenopterans, and avoid Dipterans and Arachnids. The level of this preference differed depending on the methods of food analysis used

Habitat use of Yellowhammers Emberiza citrinella, Ortolan Buntings E. hortulana, and Corn Buntings Miliaria calandra in farmland of east-central Poland

We studied the habitat use of the Yellowhammer, Ortolan Bunting, and Corn Bunting during 1995–2000 in an agricultural landscape in east-central Poland (total area of 46.5 km 2). Using the Jacobs D preference index, we found that Yellowhammer preferred woods and avoided areas with settlements. Ortolan Bunting preferred woods and avoided areas with settlements. Corn Bunting preferred grassland and wastelands, but avoided woods and areas with settlements. A comparison of the proportions of different habitat types in breeding territories of birds showed the most similarity between Yellowhammer and Ortolan Bunting, less similarity between the Yellowham-mer and Corn Bunting, and the largest differences between Ortolan Bunting and Corn Bunting. We found positive correlation between the number of wooded patches and both the numbers of the Yellowhammer and Ortolan Bunting. Yet the length of wood margins had a positive effect only on the Yellowhammer. The Yellowhammer avoided wood-field ecotones as compared with wood-grassland ecotones, whereas the Ortolan Bunting showed an opposite tendency. Habitat preferences of bunting species seem to differ in different parts of a species range. In general these three species occupied diversified farmland in Poland. Their survival will thus depend on the maintenance of habitat diversity. The planned afforestation of poor soils can reduce numbers of Corn Bunting but enhance numbers of Yellowhammer and Ortolan Bunting. Rotational fallowing of arable land will promote Corn Bunting