148 DwiGut, Moult of Quails and Grouse. Pee 
one essential difference between the moults of the Ptarmigans 
and those of the Grouse is found in the extra moult in the autumn 
by which the brown feathers regularly assumed at the usual 
periods of moult in both young birds and old are replaced by 
white ones. 
As for the prenuptial moult, it may or may not be more 
extensive than among the Grouse, the extent of renewal 
varying apparently with the latitude. Birds living in lands 
of eternal snow appear to assume very few dark feathers, 
chiefly about the head, as the brief Arctic summer sets in, 
Those of lower latitudes undergo a more extensive moult, which, 
however, never includes the remiges nor the rectrices. Besides 
this, as females seem to assume more dark feathers than do 
males, we are led to the conclusion that the Ptarmigans are a 
remarkable instance of protective coloration, and that their plum- 
age is modified to suit their environment. We know them best 
in their winter dress, snow white with black rectrices hidden by 
white coverts, and can understand how readily they harmonize 
with a snowy landscape, being thus protected from their enemies. 
With the melting of the snow they don a dusky dress mottled 
with buff, which is confined chiefly to the upper parts. A little 
later the annual moult takes place, including practically the whole 
plumage, and a reddish brown dress is assumed upon the back, 
head and breast, the remainder of the body and the wings becom- 
ing white. An extra moult shortly after removes the brown 
feathers. If white were assumed everywhere at the time of the 
annual or postnuptial moult, which begins as early as July, it 
would not be protective; but why the postnuptial moult should 
not be postponed until white would be protective, is a theoretical 
matter that need not concern us. The salient fact is the occur- 
rence of a moult similar to one characteristic of a number of the 
Ducks and observed, although not understood, many years ago. 
A description of it as noticed in the Mallard may be instructively 
read in this connection.’ Further details of this moult among 
certain Ducks have been published by Mr. Witmer Stone? and 
Mr. F. M. Chapman.® 
1 Waterton, Loudon’s Mag. Nat. Hist., VIII, 1835, p. 544. 
2 Proc. Acad. Nat. Sci. Phila., 1899, pp. 467-472. 
5 Bull. Amer. Mus. Nat. Hist., XII, 1899, pp. 231-240. 
