The brightly coloured Atlantic Puffin is well known.
However, it's less known that the iconic colours are briefly held breeding characteristics.
Until they mature at about age 5 and for most of their adult life, Puffins are much duller coloured.
This Puffin is begining to shed the outer layer of it's beak.
The white/gray facial feathers are molting, replaced by the dark gray/black feathers of the non-breeding plumage.

The sheath has separated from the bill. Light passing through the thin covering makes it look yellowish gray.
The entire sheath has moved forward and downward, partly covering the nasal opening.