EVOLUTION OF THE COLORS OF BIRDS. 143 



Specialized colors may be classed under four heads, 

 according to the degree of their development: (1) local 

 in the male sex only; (2) local in the species; (3) uni- 

 versal in the male sex only; (4) universal in the spe- 

 cies. As an example of the first may be mentioned the 

 ruby-crowned kinglet (Regulus satrapa olivacea), red- 

 winged blackbird (Agelaius), etc.; of the second, the 

 kingbird (Tyrannus tyrannus); of the third, the scarlet 

 tanager (Piranga erythromelas) ; and of the fourth, the 

 California woodpecker (Melanerpes formicivorus bairdi). 



THE PROPORTION AND DISTRIBUTION OF THE COLORS IN 

 NORTH AMERICAN GENERA. 



It may be well at the outset to take a comprehensive 

 view of the various colors as they appear among North 

 American genera. There are two hundred and nine 

 genera represented among North American birds. Black 

 is present to a greater or less extent in a hundred and 

 thirty-five, and white in. a hundred and sixty-nine of 

 them. Pure red occurs in only thirty-three genera, al- 

 though there are eighty-three besides in which it is 

 present in some such combination as reddish brown, 

 vinaceous, pink, etc., making a total of a hundred and 

 sixteen genera in which some red pigment appears. 

 Pure orange occurs in but ten genera, while yellow is 

 found pure in fifty, and in combinations such as ochra- 

 ceous in twenty-nine others, making a total of seventy- 

 nine genera in which yellow pigment is found. Green 

 is present in twenty-two genera, but in fourteen of them 

 it is metallic, and hence may not be due to a green pig- 

 ment. Green in combination, particularly with olive, 

 is found in twenty-seven genera, being metallic in only 

 two or three instances. There are accordingly about 

 thirty genera that have green pigment. Blue occurs 

 pure in twenty-three genera, in seven of which it is me- 



