They are mostly black with a white facial patch, and, typical of other puffin species, feature a very thick bill which is mostly red with some yellow and occasionally green markings. Their most distinctive feature and namesake are the yellow tufts (Latin: cirri) that appear annually on birds of both sexes as the summer reproductive season approaches. Their feet become bright red and their face also becomes bright white in the summer. During the feeding season, the tufts moult off and the plumage, beak and legs lose much of their lustre.