Vol. XXII"! Dwight, Plumage Wear and Subspecies. 37 



at the period of the last moult, California breeding birds could 

 hardly be matched by those from Alaska. 



My conclusions in regard to the American Goldfinch (Astraga- 

 linus tristis) are along this same line (Auk, 1902, pp. 149-164). I 

 stated that I could find practically no difference in color between 

 the fresh plumage of the California race salicamans and that of the 

 eastern bird. In this case, however, the eastern Goldfinch seems 

 to be the pallid race, and this is naturally to be expected, for 

 where salicamans is found on the Pacific Coast the humidity 

 averages about 10% greater than in the East. 



Some plumages and some colors yield more rapidly to wear 

 while others are practically insusceptible, especially those plumages 

 having metallic colors like the Hummingbirds or Swallows. It is 

 perhaps significant that there are few races of these and similar 

 species. The Cliff Swallow (Petrochelidon lunifrons) that builds 

 his nest in the shadow of the desert mesas differs not a whit from 

 his brother that skims the green fields of New England, nor does 

 the plumage of the Dove (Zenaidura macrura), so widely distrib- 

 uted over both humid and arid portions of the United States, 

 yield to atmospheric variations. There is, however, an odd excep- 

 tion in the case of the Purple Martin (Progne subis), of which a 

 pale race hesperia, has been described based entirely on characters 

 of the adult female. As a matter of fact she yields to climatic 

 influences only at the points (the collar, the forehead, etc.) where 

 she lacks metallic feathers. The male, on the other hand, being 

 wholly steel-blue and resistant at every point, shows no variation 

 from season to season. There does, however, seem to be one 

 slight character in the somewhat whiter tail-coverts of the western 

 female, but it does not hold in young females nor in young males, 

 both eastern and western birds having the tail-coverts equally 

 white. We have, therefore, at best, a race which rests upon one 

 weak character, peculiar to one sex, and to the adults only of that 

 sex. 



The immediate and obvious effects of humidity as a preserva- 

 tive of plumage have not been carefully estimated in individual 

 races and if a bird must be caught on its breeding ground to tell 

 what subspecies it belongs to, it looks as if there might be some- 

 thing wrong with the subspecies. Take the case of Alma's 



