JAN., 1909. BIRDS OF ILLINOIS AND WISCONSIN CORY. 39 



Back, with white spots; throat, white or whitish (immature or 

 winter). Gavia stellata. 



Red-throated Loon. 

 See No. 9. 



Back, without distinct white spots; the feathers, edged with ashy; 

 throat, white or dusky (immature or winter ). Gavia arctic a. 



Black-throated Loon. 



See No. 8. 



*GROUP 3. Wing, over 15 inches long. 



Feet, webbed; head, black, in adult; head, gray; throat, whitish, 

 in immature. Gavia immer. 



Loon. 

 See No. 7. 



Family ALCID^E. Auks, Murres, etc., etc. 



Toes, three ; no hind toe (hallux ) ; toes, palmate (full 

 webbed ) ; nostrils, separate, and not tubular. 



*GROUP 1. Wing, less than 6 inches long. 



Summer plumage: Sides of neck and stripe on side of occiput and 

 through the eye, white; rest of head, black; back, plumbeous, with 

 lateral streaks of white; under parts, white. 



Winter plumage: Head, dusky; back, plumbeous; throat and 

 under parts, white. Length, about 10 inches; wing, 5.40; bill, .65. 



Synthliboramphus antiquus. 

 Ancient Murrelet. 

 See No. 6. 



* For directions for measurement, see page 21. 



