The primary moult of Curlew Sandpipers Calidris ferruginea in North-western Australia shifts according to breeding success

Abstract

The population moult parameters, yearly onset of moult and sex-specific schedule of moult in relation to breeding success, and pattern of feather mass growth were examined in a population of Curlew Sandpipers Calidris ferruginea that migrate to northwest Australia. The mean start date of moult was 18 September, and it lasted on average 129 days. No significant variation in duration of moult was detected and feather mass was deposited at a constant rate. The yearly onset of moult was positively correlated with the proportion of first year (juvenile) birds: the mean start date of moult in good breeding years was 25 September, ten days later than mean start date of moult in poor breeding years, being 15 September. Males generally started moult five days earlier than females. The mean moult start date of males was five days earlier in poor breeding years compared to good breeding years, while the moult of females was 11 days earlier in poor breeding years compared to good breeding years. In Curlew Sandpipers the timing of post-breeding migration is advanced in bad breeding seasons, which explains the observed correlation between breeding success and the timing of moult in non-breeding areas.