moult, v. & n. (US molt)
1 intr. shed feathers, hair, a shell, etc., in the process of renewing plumage, a coat, etc.
2 tr. (of an animal) shed (feathers, hair, etc.).
--n. the act or an instance of moulting (is in moult once a year).
ME moute f. OE mutian (unrecorded) f. L mutare change: -l- after fault etc.