PATERNAL CARE IN THE EUROPEAN STARLING, STURNUS-VULGARIS - NESTLING PROVISIONING

The extent to which male birds in polygynous species with biparental c are assist in nestling feeding often varies considerably between nests of different mating status. Both how much polygynous males assist and how they divide their effort between nests may have a profound effect on the evolution of mating systems. In this study we investigated how males in the facultatively polygynous European starling Sturnus vulga ris invested in their different nests. The amount of male assistance a ffected the quality of the offspring. Polygynous males invested as muc h as monogamous males, but divided their effort asymmetrically between nests, predominantly feeding nestlings of first-mated (primary) femal es. Although females partly compensated for loss of male assistance, t otal feeding frequency was lower at primary females' nests than at mon ogamous females nests. Secondary females received even less assistance with nestling rearing, and the extent to which males assisted decreas ed with the length of the interval between the hatching of the primary and secondary clutches. These results are contrasted with those from a Belgian populations of starlings with a much more protracted breedin g season and thus greater opportunities for males to attract additiona l mates during the nestling rearing period. The results show that both the ''defence of male parental investment model'' and the ''asynchron ous settlement model'' have explanatory power, but that their validity depends on the potential length of the breeding season.