The Breeding Biology of the Brown Jay in Monteverde, Costa Rica

Abstract

In an expanding population of Brown Jays (Cyanocorax morio) in the Cordillera de Tilaran of Costa Rica, flocks exhibit a broad range of breeding behavior involving the construction of one or more nests by two or more birds, egg-laying, incubation and brooding at one nest by one or more females, and nestling care by breeding and non-breeding birds. The form that breeding behavior takes may be related to the ages of flock members. Flocks vary considerably in age, and breeding success is correlated with the number of older birds. The variation in Brown Jay breeding behavior may provide some insight into the evolution of social organization in New World corvids.