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 differencesin theproportion oftaxabetween nestsand butchering points,nestsand larders and between animal remains in pellets and larders. I studied preference by com paring the proportions of potentialprey 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

A. Golawski, Ornis Fennica 83:108-116. 2006