FAMILY ALCOVE. AUKS, PUFFINS, AND MURRES. 29 



Back, with white spots ; throat, white or whitish (immature or winter). 



Gavia lumme. Red-throated Loon. 



See No. 7. 



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

 dusky (immature or winter). Gavia arcticus. Black=throated Loon. 



See No. 6. 



* Group 3. Wing, over 15 inches long. 



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



Urinator imber. Loon. 

 See No. 5. 



FAMILY ALCID^G. 

 Auks, Puffins, and Murres. 



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

 webbed) ; nostrils, separate, and not tubular. 



* Group I. Wing, less than 5 inches long. ; 



Winter plumage : Upper parts, black ; underparts, white. In summer : The 

 breast, throat, and sides of the head and neck, sooty brown. 



Alle alle. Dovekie. Little Auk. 



See No. 17. .^' 



* Group 2. Wing, 5.50 to 6.50 inches long. 



Bill, parrot like; underparts, white; back, black; usually a black 

 collar. Fratercula arctica. Puffin. Sea Parrot. 



See No. 9. 



Adult in summer : General plumage, black, a white patch on 

 the shoulder; basal half of the greater wing coverts (feathers 

 forming the white patch on the wing), black. Winter birds have 

 the underparts white, and the upper parts, black and white. 



Cepphus grylle. Black Guillemot. Sea Pigeon. 



See No. 11. 



Similar to Black Guillemot, but has the wing coverts (feathers forming the white wing 

 patch) entirely white and not with basal half black. 



Immature and winter birds (except wing coverts), resembling the Black Guillemot. 



Cepphus mandtii. Mandt's Guillemot. 



See No. 12. 



* For directions for measurement, see page 9. 



