Note 7 — Chapter VII

For an introduction to this example I am indebted to Mr. W. D. Miller of the American Museum of Natural History. Some account of the facts is given by Baird, Brewer, and Ridgway (A Hist. of N. Amer. Birds. 1874, II, pp. 540, 544, etc.). S. varius occupies the whole country in suitable places from the Atlantic to the eastern slopes of the Rockies, and all Mexico to Guatemala. S. nuchalis was first known from the Southern Rockies only, but many were afterwards taken in Utah. S. ruber is restricted to the Pacific coast. In Ridgway's opinion all three are geographical forms of one species. In ruber the sexes are alike having both a great extension of the red in the throat, and a red crescent. The male of nuchalis grades to the ruber form, but the female does not. This female has some red in the throat like the male of varius, whereas the female of varius has a whitish throat.