66 Birds of Colorado 



by their shorter necks, and from the Ducks by their 

 reticulate tarsi ; the sexes are alike and the hallux or 

 hind toe is simple and not lobed. 



Key of the Genera. 



A. Bill and feet always black. Branta, p. 6S. 



B. Bill and feet not black, usually pink or yellow. 



a. Depth of bill at base more than the length of the culmen ; 



pluniage mainly white. Chen, p. 66. 



b. Depth of bill at base less than half the culmen ; plumage 



never mainly white. Anser, p. 68. 



Genus CHEN. 



Bill about equal to the head, high at the base, its depth there more 

 than half the length of the culmen ; serrations on the cutting-edge 

 of the upper mandible prominent, large and fully exposed ; plumage 

 chiefly white, or white and grey ; bill and feet red. 



Four species, chiefly in the Arctic regions of the Northern Hemisphere. 



Key of the Species. 



A. Outline of the frontal feathering forming a convex line at the 



base of the bill. 



a. Larger ; wing over 17. C. h. nivalis, p. 67. 



b. Smaller ; wing imder 17. C. hyperboreus, p. 66. 



B. Outline of the frontal feathering nearly straight ; size still 



smaller, wing about 14-5. C. rossi, p. 67 



Snow-Goose. Chen hyperboreus. 



A.O.U. Checklist no 109 — Colorado Records — Henshaw 75, p. 470 ; 

 Thorne 87, p. 264 ; Morrison 89, p. 165 ; Cooke 97, pp. 18, 58, 196; 

 06, p. 65 ; Henderson 03, p. 234 ; 09, p. 226 ; Rockwell 08, p. 158. 

 a Description. — Adult — Pure white except the wing, the tips of which 

 are black and the bases grey ; heeid often stained with rusty-brown ; 

 iris dark brown, bill dull red with a white tip and black along the 

 cutting-edge; legs dull pink. Length 25-0; wing 17-0 or less; tail 

 5-5 ; culmen 2-3 ; tarsus 3-1. 



Yoimg birds have the top of the head and upper-fjarta light grey, 

 and the bill and feet dark. 



Distribution. — Breeding on the Arctic coasts of the Mackenzie 

 Province and probably in north-east Asia ; wintering from the Mis- 

 sissippi Valley to California and south to central Mexico ; in Asia 

 to Japan. 



