A tufted puffin sheds part of its bright bill for winter
In summer, a tufted puffin grows a colorful outer bill plate along with golden head plumes and a white face mask. After the breeding season, the plate falls off, the plumes disappear and the bill becomes smaller and duller.
The summer accessories come off, and the winter puffin returns in sensible brown.
Source · Seattle Aquarium ↗