Food Provisioning in the Pied Flycatcher: Do Females Gain Direct Benefits from Choosing Bright-Coloured Males?

Abstract

We studied individual variation in the performance of parental care of male pied flycatchers Ficedula hypoleuca in a woodland area near Oslo, Norway. During a 24-h period of enforced female absence, we recorded male feeding rate and nestling growth, as well as changes in male body mass. Using a matched-pairs comparison we found that older males were more successful in feeding the young than 1-year-old males, even when plumage colour or breeding experience were similar. These results may be explained by increased skill due to age or condition-dependent mortality, rather than increased parental effort, since young and old males lost equal body mass during the period of female absence. Overall, bright-coloured males and males with previous breeding experience performed better in terms of increased brood mass, than dull-coloured males and males without previous breeding experience, respectively. These results were not significant when we only compared males of similar age, but the sample sizes were small in the latter comparisons. Bright-coloured males also tended to lose less body mass when they were left to feed the brood alone than did dull-coloured males, indicating that the higher performance was not due to a higher parental expenditure. We argue that females that choose old males as mates benefit in terms of a mate that is capable of a high performance of parental care. Females may use male plumage colour as an indirect cue in assessing male age, since the plumage becomes brighter with age. Despite differences in brood-mass changes during female absence, there was no difference in feeding rate between first-year and older males, nor between dull- and bright-coloured males. This shows that feeding rate may be an inadequate measure of the variation in individual ability to nourish the young.