Kleptoparasitism, in which an individual steals food from other individuals of the same or a different species, is frequent in birds and represents a form of direct competition that can potentially influence the structure of communities. We addressed this idea by analyzing the foraging behavior and the spatiotemporal patterns of use of a refuse dump by four species of corvids: the Rook (Corvus frugilegus), Carrion Crow (C. corone), Eurasian Jackdaw (C. monedula), and European Magpie (Pica pica). Carrion Crows showed a unique degree of specialization in kleptoparasitism, allocating most of their time to scanning from the periphery of the dump and attacking other individuals rather than searching directly for food on the refuse. During winter, when the presence of corvids was highest, the species segregated through different timing of visits to the dump: Rooks and Eurasian Jackdaws were most abundant in the early hours, Carrion Crows in the middle of the morning, and European Magpies in the early afternoon. We suggest that kleptoparasitism played a role in shaping the temporal assemblage of species in the dump. On one hand, Carrion Crows matched the daily pattern of abundance of their main hosts, the starlings (Sturnus spp.), thus increasing their opportunities for kleptoparasitism. On the other hand, European Magpies' delayed arrival prevented overlapping with Carrion Crows, which reduced their risk of being robbed and, therefore, enhanced the efficiency of foraging. Temporal segregation of species has rarely been reported among vertebrates, but our results suggest that it may be an important mechanism of coexistence on spatially clumped food resources.
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Vol. 126 • No. 3