226 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



while those from the more elevated localities are perceptibly smaller 

 and have a denser, closer litting plumage. 



During the wintex season the entire plumage is white with the excep- 

 tion of the tail, and in some of the males of L. niutus, also the greater 

 number of the females, a black stripe from the base of the side of the 

 bill produced through the eye to the auricular legiou. This black 

 stripe, however, varies in position and distribution. When nearly ob- 

 solete it occupies the auricular region, and when greatly developed is 

 continuous across the forehead of the bird, and is even present in the 

 summer plumage of some females. This feature is specially charac- 

 teristic of the winter plumage alone, however, and at this season it is 

 almost impossible and even hazardous to assert that this or the other 

 example is to a certainty this or that race. The table of measurements 

 liroves only such variability of size as may be met with in individuals of 

 any other series of birds belonging to the same species. 



The summer plumage is assumed at variable periods of the months of 

 April, May, or even in early June, according to the locality. The moult 

 for the summer is usually shown first on the head and neck, followed 

 by the lower back, sides, breast, middle back, lianks, and abdomen, in 

 the order named. The abdomen and chin are the last areas to show 

 the complete moult. The parts named are also the first to assume, in 

 the order given, the white winter plumage. 



During the time of the summerplumage scarcely a single day passes but 

 that tlte general color of the feathers is not modified by the appearance 

 or loss of some feather. How, then, is it possible to state just where 

 the plumage of an individual shall constitute the summer stage when 

 it is scarcely possible to find two birds of the same sex, age, and local- 

 ity which do not differ in an appreciable degree of coloration, and 

 where there are no other characters on which to base a comparison ? 

 In the examples just compared I find the plumage of birds from Nor- 

 way, France, Switzerland, and two localities in the "Barren Grounds" 

 of Arctic America which do not vary in an essential color, and the pat- 

 tern of coloration scarcely more divergent than will be found in birds 

 of the same sex from the same locality of either region mentioned. 



The birds from the western coast of Arctic America and the east- 

 ernmost Aleutian Islands do not, so far as I can see, differ appreciably 

 from the European specimens in point of plumage during the breeding 

 season. The males perhaps show a slight variation in shade of the 

 ground color, but not in an essential degree. Hence the American and 

 the European bird should be separated only as races, if at all, although 

 most authors who have separated the American bird have distinguished 

 it as a species by a binomial appellation — Lagoims rupcstris (Clm.) Leach. 



It seems to me, however, that the European birds mutus and alpinus 

 should constitute, as is held by many authors, but a single species 

 having the name Lagopus mutus Leach, while the American bird may 



