PARENTAL CARE AND POLYGYNY IN THE CHIFFCHAFF PHYLLOSCOPUS-COLLYBITA

The males of most bird species help to raise the young, and females ma y suffer costs from polygyny because of having to share the male paren tal care. In the chiffchaff (Phylloscopus collybita) nests of monogamo usly and polygynously mated females had similar success in relation to the proportion of fledged young. Overall, male chiffchaffs provided l ittle assistance to females during the nestling period, but they incre ased help when the young left the nest. Females who choose already-pai red males (secondary females) incurred lower reproductive success, bec ause they were unable to start a second brood after raising their firs t brood. Primary and monogamous females which received male help in th e form of food provisioning during the fledgling period were more like ly to attempt a second brood. This is the first study that reports ass ociated costs to secondary females due to the lack of paternal aid aft er the young have fledged the nest. However, secondary females still c an obtain compensatory benefits, as predicted by the polygyny threshol d model, since most of them settled in good quality habitats, close to the primary females.