48 Nichols, Recognition Marks in Birds. [jan. 



close proximity, marmots, coneys, and a spermophile, striped some- 

 thing like a high-colored chipmunk. The marmots and coneys, 

 harmonizing in color with the gray rock slides, are continually 

 advertising their presence by persistent whistling and bleating. 

 The conspicuously colored spermophile is silent. 



In conclusion, the writer's observations foster the belief that 

 advertising and concealing colors, each in its own way, are of value 

 to a bird, and that the bird's plumage is determined as a compromise 

 between the two adapted to its particular needs and habits. Proba- 

 bly there are other forces also acting more or less to determine 

 the colors, as adaptation to light. Birds living in insufficient light 

 have, as a rule, dark colors which absorb, those in superabundant 

 light, lighter colors which repel it. 



