138 THE STORY OF A BIRD LOVER 



That many good field-ornithologists declare that 

 they have seen Brewster's warbler attending to 

 young seems an answer in itself to the hypoth- 

 esis of hybridity, did not the number of indi- 

 viduals in themselves controvert such a premise. 

 Hybrids do occur among wild birds, but are 

 casual. 



If then it is conceded that it is improbable 

 that over a hundred cases of wild hybridity have 

 been recorded between the golden-winged and 

 blue-winged warbler, the dichroic hypothesis 

 remains. Granted that this bird and the other 

 two are all one kind with several dichroic phases, 

 this particular example of the dichromatism, which 

 is now of measurable occurrence and quantity, 

 apparently did not occur at all early in the last 

 century, was not secured until 1862, not recognized 

 till 1875, and from that time on has grown in a 

 geometrical ratio. That may be, but I am more 

 inclined to believe that in Brewster's warbler we 

 have the beginning of a new form of organic life. 

 That such forms, especially when based on exter- 

 nal color, should present wide individual variation 

 in their early history seems probable. Brewster's 

 warbler does show such variation. That a long 

 period must elapse before the bird's standard of 

 appearances becomes fixed so as to be within the 

 conventional limits of variation observable in 

 well-defined forms, seems obvious. 



