Food information in the Black-headed Gull, Larus ridibundus

Abstract

The ‘information-centre’ hypothesis suggests that bird colonies function as sources of information about good feeding sites, to which unsuccessful birds may follow foragers. One assumption of the hypothesis is that unusually successful foragers are followed by other colony members when returning to a newly found, rich food source. We tested this assumption in a colony of Black-headed Gulls (Larus ridibundus). Parents feeding their young from a rich, artificial food source were observed on their return trips to the feeding site. In none of 50 cases did other colony members follow them to the newly found food. However, the gulls were attracted to groups of foraging conspecifics. In experiments with paired food piles and a group of model gulls at one pile in each pair, Black-headed Gulls always alighted first at the piles with models. Hence the information-centre mechanism was refuted, but the gulls did acquire food information from each other in another way.