CLASS, A.M.*; CHAVES-CAMPOS, J.; Virginia Tech; Purdue University: Breeding behavior and nest site selection of the Ocellated Antbird Phaenostictus mcleannani

Basic knowledge of the natural history of species is essential to our understanding of reproductive biology. Our understanding of tropical bird natural history is particularly poor. Tropical obligate ant-following birds track army ant colonies foraging from arthropods flushed by their raids. However, many of these birds nest close to the ground, thereby risking nest predation by army ants. Here we evaluate whether Ocellated Antbirds nest purposefully away from the range of army ant colonies and provide the first description of behavior at the nest for this species. Six nests were found at La Selva Biological Station, Costa Rica, in 2004-2005. All nests were below one meter from the ground, between buttress roots of trees, supporting the only other published description of a nest of this species. Parents brought an overabundance of prey from swarm raids to the nest, when fair weather allowed ants to forage, and stashed excess prey in the nest cup. This observation suggests that reproductive success can be determined by the birds� ability to find raids actively flushing abundant prey. The nests were located significantly away from the reach of nearby army ant colonies, i.e. more than 100 m, but a colony in non-nomadic phase was no farther than 200m from each nest. Nesting close to a sedentary colony may decrease nest predation by nomadic raids because army ant colonies apparently avoid each other�s chemical trails. We also found that the nests were closer to trails and streams than what chance would predict, suggesting that such visual landmarks may be used in navigation. We propose that the location of army ant colonies and visual landmarks may be important factors in nest site selection of obligate army ant-following birds.