The Audubon Societies 261 



difficulty of bird-study, if also to the interest, for everyone has had the ex- 

 perience, occasionally, of being unable to distinguish the colors of a bird even 

 though at close range. It doubtless also accounts for many of the strange 

 descriptions of birds that one receives from young observers. 



Some authorities claim that a black pigment is also to be found in the 

 feathers of birds, but when the brown pigment is very dense it appears black, 

 and it seems impossible to distinguish between the two. Occasionally an 

 excess of this brown or black pigment develops in the feathers of an individual 

 which will make it appear much darker than the other members of the same 

 species. This is called melanism, (from the Greek melas, meaning black) and 



A NORMAL MEADO^^XARK AND AN ALBINO 

 Albinism is due to lack of pigment caused by some physical weakness 



apparently it can be brought about by subjecting moulting birds to extreme 

 humidity. In nature, regions of extreme humidity usually produce darker 

 races of birds than arid regions. Thus, the sooty Song Sparrow of the Pacific 

 Coast is so much darker than the Desert Song Sparrow of Arizona that one 

 would not hesitate to call them distinct species were it not for the fact that 

 their color patterns are identical. The dark and light phases of the Rough- 

 legged Hawk are another example of melanism, but even more familiar is the 

 case of the black and gray squirrels, examples of each occurring in a single 

 litter of young without reference to sex or vigor. In this case humidity can 

 play no part though it is said that the black phase was formerly more abundant 

 when the country was heavily forested, and it is still the dominant form where 

 the primeval timber exists, while the gray phase is the abxmdant form of the 

 wood-lot and open country. 



The opposite of melanism is albinism (from the Latin albus, meaning white). 

 It is caused by an absence or degeneration of the pigment. Pure albinos are 



