Paternal care in the European starling, Sturnus vulgaris: incubation

In polygynous passerines, males of some species provide food for their nestlings, but male incubation seems to be rare. In the European starling both the mating system and the extent to which males help with incubation vary. This enabled the relationship between mating system and male incubation to be investigated. The extent to which males provided care to a particular nest depended on mating status: monogamous males incubated more than polygynous males did in any of their females' nests. On average, bigynous males incubated as much in their two nests as monogamous males did in their single nest, but polygynous males who invested in only one of their nests incubated less than monogamous males. Females partly compensated for the variation in male incubation, but still nests of polygynously mated females were attended less. Polygynous males invested more in the nests of the first females mated with (primary female) than in the nests of later settling females. Secondary females received less help the later they laid their eggs in relation to the mate's primary female. Bigynous males that incubated in both their nests invested more in the nests of their primary females the earlier these eggs were laid in relation to those of the secondary females. Male help with incubation may affect a female's fitness, both because increased attentiveness resulted in shorter incubation times and because females receiving less help may pay a higher cost in terms of energy expenditure. Hence, there will be a conflict between polygynously mated females over paternal incubation.