FAMILY GAVIIDA.— LOONS. 27 
FAMILY GAVIIDA. 
Loons. 
Toes, four; front toes, palmate (full webbed) ; bill, pointed ; 
tarsus, flattened; hind toe, with fiap or small lobe. 
* Group 1. Wing, 9.50 to Ili inches lone. 
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. 
Head, ashy gray; throat, black (adult). Gavia arcticus. Black-throated Loon. 
See No. 6. 
Throat, gray; front of neck, chestnut brown (adult). 
(ravia lume. Red=throated Loon. 
See No. 7. 
ais 
*QGroup 2. Wing, 11 to 15 inches long. 
Section |. Depth of bill at base, more than .85. 
Head, black (adult). Gavia imber. Loon. 
See No. 5. 
Top of head, grayish; throat, white (immature or winter plumage). 
Gavia imber. Loon. 
See No. 5. 
Section 2. Depth of bill at base, less than .85. 
Head, ash gray; throat, black (adult). Gavia arcticus. Black-throated Loon. 
See No. 6. 
Throat, gray; front of neck, chestnut brown (adult). 
Gavia jumme. Red=throated Loon. 
See No. 7. 
* For directions for measurement, see page 9 
