Kleptoparasitism in Common Guillemots at two colonies during a period of poor food availability

Kleptoparasitism, the stealing of food items from other animals, is an important foraging strategy for many taxa. In many cases the kleptoparasites and hosts are different species but less commonly, prey items are stolen from conspecifics. Recent studies have highlighted the potential importance of intra-specific kleptoparasitism in food-stressed populations, and here we show facultative kleptoparasitism at two North Sea colonies of Common Guillemots Uria aalge during one year of poor breeding success and one year of near average breeding success. The frequency of kleptoparasitism differed between colonies and years, reflecting variation in the magnitude of the benefits from kleptoparasitism, which was probably associated with variation in prey availability at sea. Specialised foraging strategies such as kleptoparasitism may allow individuals to buffer adverse conditions more effectively than those foraging only at sea