Diet composition and spatial patterns of food caching in wintering Great Grey Shrikes (Lanius excubitor) in Bulgaria

Abstract: Diet composition of the Great Grey Shrike (Lanius excubitor) was studied on the basis of cached prey, pellets and food remains collected beneath perches, from November to March for 5 years (19982002). The ratio of vertebrates and invertebrates (by numbers) was nearly 1:9. Pellet dimensions were on average 25.4 (–5.45) mm × 10.8 (–1.13) mm. A total of 104 caches were found, including 95 with Gryllus campestris. Most caches were fixed on plants (91.3%) and the rest on barbed wire. Stored prey items were placed at an average height of 1.05–0.29 m (range 0.571.9 m) above ground, most commonly in the middle part of the plants. Storage height was significantly correlated with plant height. Patterns of impaling were also studied about half of the specimens of G. campestris were impaled through the forepart of the abdomen. A latitudinal cline in the proportion of vertebrates in the Great Grey Shrike diet during winter in Europe proved to be statistically significant