Cooperative Breeding in the Campo Flicker I

. Cooperative breeding and complex social systems are known in woodpeckers, but most available information concerns species of the North Temperate Zone. The social behavior and breeding ecology of tropical woodpeckers are poorly documented. Here we present data on the breeding behavior and ecology of a tropical woodpecker, the Campo Flicker (Colaptes campestris campestris). We confirm for the first time, through behavioral observations, facultative cooperative breeding in this species. Both males and females were observed visiting the nest during the incubation and nestling period. In cooperative groups some helpers were identified as young from the previous year, but others seem to be unrelated individuals that joined the groups. In addition, our behavioral observations strongly suggest both polygyny (a male breeding with more than one female simultaneously) and joint nesting (multiple females contributing eggs to a single nest) in some but not all cooperative groups. These observations reveal a complex social system in this tropical species, with high potential for reproductive conflicts both within and among groups, due to the presence of new potential breeders or through advantages emerging from the effects of group size.