Pre-breeding moult in adult Black GuillemotsCepphus grylle

The progression of pre-breeding moult in adult Black Guillemots Cepphus grylle was observed at Bangor, Co. Down. Moult began as soon as early November, which is much earlier than more northerly populations in the UK. Moult was completed within ten weeks. Early return to the breeding colony and early moult may help individuals to obtain breeding sites.