Two cooperative breeding cases in Lesser Spotted Woodpecker Dendrocopos minor

Abstract

During a study of a colour-marked population of Lesser Spotted Woodpecker (LSW) in NE Spain we found two cases of cooperative breeding, in which two females and a male were rearing the brood. One of the females was involved in both cooperative breeding cases, in two consecutive years. We analysed the feeding contribution of each individual to nestling care as well as feeding rates to nestlings. In both cases the male showed a (compensatory) reduction in nestling feeding due to the involvement of the second female. Total feeding rate increased slightly compared to regular (noncooperative) monogamous pairs. The high breeding success found in the second case (six eggs/six nestlings) is thought to be due to the cooperation of the three adults in nestling care. The two cooperative breeding cases were found in territories that suffered from significant selective logging of dead trees. This logging is thought to be a possible anthropogenic example of the ecological constraints hypothesis and a significant factor that could force atypical cooperative breeding attempts. A locally biased sex-ratio might result in the cooperation of two females and a male in both cases. No evidence of kinship was found among members of the cooperative breeding teams. We could not determine whether the cooperative breeding cases were monogamous or polygamous.