EVOLUTION OF THE COLORS OF BIRDS. 177 



blend more or less at the point of meeting. This is the 

 case in the vermilion flycatcher {Pyrocephalus rubhieus 

 mexicanus) , where the scarlet feathers along the border 

 of the crown are brown, basally, but the two colors are 

 not sharply separated on the feather. This is also the 

 case with the white and slate-colored hybrids of Jv.nco 

 hyemalis. 



Besides these hybrid feathers, which help to define 

 patches of color on the bird, there are other feathers 

 which are of two or more colors, but which are of no 

 apparent utilitarian significance. These I have called 

 pseudohybrids. They are especially interesting as 

 showing the sort of material furnished to natural 

 selection with which to produce effects. It is evi- 

 dent that along the line of demarcation of two colors 

 the pigments are apt to get confused as to which is their 

 proper route, and hence both come upon the same 

 feather, by accident, as it were. Natural selection 

 has frequently used this chance commingling for the 

 production of effects, but has not always done so. 

 Thus true hybrids are almost wanting in the crown 

 patches of th« goldfinches, but pseudohybrids are 

 not uncommon. They are feathers in which the black 

 of the crown and the olive of the back are both 

 present, but instead of helping to define the black patch 

 they rather tend to break up the symmetry of its bound- 

 ary. This is especially noticeable in specimens of 

 Spinus psaltria and S.la^vrencei. In the latter the feath- 

 ers along the edge of the crown patch are pseudohybrids, 

 and the same is true of those between the yellow and 

 gray of the breast. 



Another class of sharply marked pseudohybrids are 



those in which one color is completely concealed by 



overlapping feathers. Such pseudohybrids are very 



common and are interesting as being in most instances 



12 



