Abstract.—By examining specimens of ptarmigan (Phasianidae: Lagopus spp.), I
quantifi ed three discrete periods of molt and three plumages for each sex, confi rming
the presence of a defi nitive presupplemental molt. A spring contour molt was
signifi cantly later and more extensive in females than in males, a summer contour
molt was signifi cantly earlier and more extensive in males than in females, and
complete summer–fall wing and contour molts were statistically similar in timing
between the sexes. Completeness of feather replacement, similarities between the
sexes, and comparison of molts with those of related taxa indicate that the white
winter plumage of ptarmigan should be considered the basic plumage, with shi