Reproductive Success and Nest-Site Selection in a Cooperative Breeder: Effect of Experience and a Direct Benefit of Helping

Abstract

We determined whether nest-site characteristics influence reproductive suc- cess and whether experience influences nest-site selection in a population of cooperatively breeding Long-tailed Tits (Aegithalos caudatus). Nest predation was high; only 17% of breed- ing attempts resulted in fledged young. The height of nests was an important determinant of success; low nests were significantly more successful than high nests. A breeder's age, natal nest site, and breeding experience had no significant effect on nest-site selection. How- ever, failed breeders who helped at the successful nests of conspecifics built subsequent nests lower than nests built prior to their helping experience. Failed breeders who did not help showed no reduction in the height of subsequent nests. Moreover, the subsequent repro- ductive success of failed breeders who helped was significantly higher than that of failed breeders who did not help. We conclude that helpers gain information on nest-site quality through their helping experience and thus gain a direct fitness benefit from their cooperative behavior. We suggest that experience as a helper offers a more reliable cue to nest-site quality than breeding experience because helpers are associated with nests only during the nestling phase when few nests are depredated. In contrast, although successful breeders may expe-