378 



Grinnell, Chestniit-backcd Chickadee. 



TAuk 



Ljuly 



somewhat darker than in the corresponding age of barlowi, and 

 moreover is more nearly like the juvenal plumage of riifescens. 

 But the sides in adult rufescens are deep brown, almost chestnut, 

 while the young has much paler, merely dark rusty sides. And 

 what is most significant is that the young of rufescens and hud- 

 sotiicHS are much nearer alike than are the adults, the former 

 having only very slightly darker rusty on the flanks. The young 

 of hudsonkus in respect to intensity of browns almost exactly 

 equal the adults of the same species, showing that the present 

 coloration is of very long standing, and offering further evidence 

 that hudsonicus is nearest the common stock form of all the chicka- 

 dees under consideration. Juvenal characters, resembling ancestral 

 conditions, lag behind the newer acquired adult characters. 



To repeat : The young of barlowi has the sides paler rusty 

 than neglecius, negledus slightly paler than rufescens, but rufescens 

 has the sides slightly more rusty than hudsonicus, a sequence 

 which accords well with the present theories of origin. (See 

 Map III.) 



Measurements (in Inches and Millimeters) of the Races of 

 Parus rufescens. 



J 



