How consistently are good parents good parents?: Repeatability of parental care in the house sparrow, Passer domesticus

In many avian species, substantial individual variation occurs in parental food-provisioning levels, which often is assumed to reflect variation in parental quality. Parental quality also has often been invoked as a key element in mate choice among biparental species, and many sexually-selected traits have been investigated as potential predictors of parental quality. In recent studies of house sparrow (Passer domesticus) parents, we found that individuals behaved remarkably consistently across time, regardless of temporary manipulations of the nestling provisioning of their partners. This suggests that variation in parental competence may be attributable to quality differences among individuals. One prediction of the 'parental quality differences' hypothesis is that individuals also should show consistency in their provisioning behavior across broods. To test this, we compared the parental delivery rates of individual house sparrows across broods. Parents of both sexes reduced their per-chick delivery rates as the season progressed; parents of both sexes were also responsive to changes in their brood sizes. Despite these sources of environmental variation in provisioning rates, the parental care of individual males was highly repeatable across broods. By contrast, female parental care showed extremely low repeatability, and standardized measures of among-individual variation in parental behavior revealed females to be much less variable than males. These results indicate that females in this multi-brooded species have much to gain from mate-choice decisions predicated on male parental quality or accurate indicators of such, whereas males are less likely to profit from being highly selective about the 'parental quality' of their partners.