Azure-winged magpies, Cyanopica cyana, 'parasitize' nest defence provided by Japanese lesser sparrowhawks, Accipiter gularis

Abstract

Abstract. A field experiment with simulated nests of azure-winged magpies was carried out to test the hypothesis that this species nests in association with Japanese lesser sparrowhawks in order to reduce nest predation while paying few costs. The predation rate on nests was lower within 50 m of a hawk's nest during the incubation to nestling period than it was further away or at other stages of the breeding cycle. In addition, there was an inverse relationship between nest predation rate and hawk defence effort. Observations of natural nests showed that magpies did not defend their nests when nesting close to a hawk, and that hawks rarely preyed on magpies. Thus, magpies benefited from nesting close to hawks, while paying few or no costs.