EVOLUTION OP THE COLORS OF BIRDS. 273 



FAMILY STKIGID.E. THE BARN OWLS. 



GENUS STRIX. THE BARN OWLS. 



(1) Male like female; young like adult. 



Prevailing colors, ochraceous yellow, grayish, white. 



The snowy whiteness of the face, and sometimes the 

 breast, of this bird I take to be a socialistic recognition 

 mark, which would be useful in their social intercourse 

 at night, in the darkness of their nesting place, etc. 

 What the use of the mottlings may be, or the general 

 color of the back, I am unable to suggest. 



FAMILY BUBONID.E. THE HORNED OWLS, ETC. 



The color markings of this family are of a very un- 

 modified order of development, as might be expected in 

 a group of nocturnal birds. Two features are noticeable 

 with regard to the coloration: (1) the absence of any ten- 

 dency towards melanis^n as among the hawks, but rather 

 the reverse tendency towards albinism; (2) the absence 

 of a tendency towards a uniform color as among the 

 hawks, but rather an inclination towards a retention of 

 the mottled plumage. Glaucidium is an exception to 

 this latter rule, however. This tendency towards albin- 

 ism in a group of birds habitually living in the dark, 

 and towards melanism in an allied group which live in 

 the light and with little selective influence to restrain 

 the deposition of pigment, would seem to be in accord- 

 ance with the influence of light upon the development 

 of pigment. Still, other causes have doubtless been 

 instrumental in bringing about this result, for the whitevr 

 ness becomes most pronounced towards the arctics where 

 it would be most needed for protection, whereas in more 

 southern latitudes it is a useful form of recognition 

 mark. 



The different genera present some interesting features 

 18 



