Postnuptial moult in a Belgian population of Nuthatches Sitta europaca

Postnuptial moult was studied in three consecutive years in a small population of Nuthatches. Fourteen to 25 individuals were captured in active moult each year with an average of 2.1 captures per bird per season. The total duration of moult was estimated as 88 days. Secondary moult was completed a few days after the end of primary moult. Primary moult rate was maximal at the beginning of moult, because many feathers were then growing simultaneously. Individual differences in the timing of moult were small, with a maximal spread of 21 days, and there was little variation between years. No differences in moult were found between sexes or age classes. Birds with failed broods moulted before successful breeders and early breeding females before late breeders. Duration and timing of moult are compared with other resident passerine species. A hypothesis based on summer territorial behaviour is put forward to explain the high degree of synchronization within the population and the relation between breeding and moulting.