The timing of moult in Black GuillemotsCepphus gryllein Shetland

Abstract

The sequence and timing of moult in Shetland was similar to that found for the same subspecies in western Scandinavia. Winter sea surface temperature is similar in these areas and is probably a key factor affecting the timing of the spring body moult. Immatures began the spring moult later than, and the full autumn moult earlier than adults. Adults are flightless for 4–5 weeks, mostly during September, when they congregate in moult flocks.