Biometrics and post‐juvenile moult in the Goldcrest Regulus regulus

Abstract

Goldcrests caught inland in Cleveland and on the Isle of May, Scotland had significantly shorter wings than migrant birds caught on the east coast of Cleveland, suggesting that continental birds had longer wings than those of the British population. Duration of post‐juvenile moult (and wing shape) was similar to that found in short distance migrant Sylvidae, which are closely related (Beaman 1994), but the extent of this moult was more in line with the longer distance migrant Sylvidae species and very dissimilar to resident birds in Britain. It is suggested that the reason for an abbreviated post‐juvenile moult is not time constraints after fledging but may be a cost effective method to conserve energy resources due to their small size. Body mass did not differ significantly at any site suggesting no undue loss or gain in mean weight. A non‐significant mean increase in body mass occurred during the mid post‐juvenile moult stage, coinciding with the time when most growing feathers were present.