THE PLAINS AND COLORADO 137 



these birds in different collections. In certain 

 regions, notably at Englewood, New Jersey, and 

 in parts of southern Connecticut, they may be 

 seen every year during the breeding season 

 with certainty. Every good naturalist who has 

 worked recently in the lower Hudson River 

 valley has met with some of these birds. So 

 it is a tangible part of the fauna of eastern 

 North America now, and its presence can be 

 readily detected in given localities at definite 

 times of the year. 



It does not seem probable that a form so com- 

 mon as this, and ranging over as large an area as 

 from Pennsylvania to Massachusetts, should have 

 remained unknown to our earlier ornithologists: 

 such keen field-naturalists as Audubon and 

 Wilson, Baird, Cassin and Lawrence, Coues and 

 Prentiss. Nuttall made careful and prolonged 

 study of birds in the region where Mr. Brewster's 

 type was collected. Yet none of these close 

 observers and good collectors either recorded or 

 collected this bird. The presumption is that the 

 birds could not have been so common early in the 

 nineteenth century as they are now, if they were 

 represented at all at that time. Nor does it seem 

 that either the theories of hybridity, or that of 

 dichromatism, are sufficient to account for this 

 kind of bird. Fertile hybrids are practically 

 unknown either in wild or domesticated birds. 



