FAMILY GAVIID^E. LOONS. 27 



FAMILY QAVIIDyE. 



Loons. 



Toes, four; front toes, palmate (full webbed) ; bill, pointed; 

 tarsus, flattened ; hind toe, with flap or small lobe. 



* Group 1. Wing, 9.50 to 1 1 inches long. 



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



Gavia lumme. Red throated Loon. 



See Xo. 7. 



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

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



See Xo. 6. 



Head, ashy gray ; throat, black (adult). Gavia arcticus. Black=throated Loon. 



See Xo. 6. 

 Throat, gray; front of neck, chestnut brown (adult). 



Gavia lumme. Red-throated Loon. 



See Xo. 7. 



* Group 2. Wing, 1 1 to 15 inches long. 

 Section 1. Depth of bill at base, more than .85. 



Head, black (adult). Gavia imber. Loon. 



See Xo. 5. 



Top of head, grayish; throat, white (immature or winter plumage). 



Gavia imber. Loon. 

 See Xo. 5. 



Section 2. Depth of bill at base, less than .85. 



Head, ash gray; throat, black (adult). Gavia arcticus. Black-throated Loon. 



See Xo. 6. 



Throat, gray ; front of neck, chestnut brown (adult) . 



Gavia lumme. Red=throated Loon. 



See Xo. 7. 



* For directions for measurement, see page 9. 



