Antbirds parasitize foraging army ants

In the tropical forests of Central and South America, army ants of the Ecitonini tribe, and the numerous animals that follow them through the understory, share a complex relationship that has far-reaching effects on population dynamics and community structure. Although considerable study has been made of various participants in this relationship, no research has explicitly examined the nature of the interaction between the ants and the most important group of followers, the ant-following birds. Here we show, through use of exclusion experiments, that ant-following birds are parasites on Eciton burchellii, significantly reducing the ants' success rate in capturing prey. This has important implications for our interpretation of ant behaviors during swarm-raiding, competitive interactions among the ant-following birds, and possibly also the relative abundance of those social hymenopterans that are typically preyed upon by army ants.