Reproduction and moult in pied and collared flycatchers (Ficedula hypoleuca and F. albicollis) : A life-history approach

Abstract: This thesis examines the trade-offs between investments in reproduction and self-maintenance (moult) in pied and collared flycatchers (Ficedula hypoleuca and F. albicollis). These two long-distance migratory passerine bird species were studied on the breeding grounds in Fennoscandia and in England.Passerine birds, such as pied and collared flycatchers, usually start moulting soon after breeding. However, in this study a temporal overlap between reproduction and moult was found in both species. Adult birds with moult-breeding overlap suffered reduced fitness, both in terms of reproductive success and survival probability, indicating trade-offs between reproduction and moult. However, collared flycatchers with experimentally increased reproductive investment initiated their moult at the sametime as those for which the reproductive investment was experimentally reduced. Thus, in this case no trade-off between reproduction and moult was identified.In both species, males more often than females showed a moult-breeding overlap. Moreover, female pied flycatchers were found to have a more fixed time-table for reproduction and moult than males. The sexual difference in timing of moult suggests a sexual conflict over allocation of resources for reproduction and moult, respectively. Female pied and collared flycatchers mated to males with moult-breeding overlap had a lower survival probability than females mated to non-moulting males. These females probably had to increase their reproductive investment as a result of their males starting to moult.The timing of breeding and moult was compared among three Fennoscandian populations of the pied flycatcher. In all three populations and in both sexes, reproduction and moult overlapped. However, contrary to what has been assumed, this overlap did not become more pronounced with increasing latitude. This suggests that long-distance migrants breeding at high latitudes employ other strategies than moult-breeding overlap to compensate for the short breeding season.