284 FIELD MUSEUM OF NATURAL HISTORY -ZOOLOGY, VOL. IX. 



8. Gavia arctica (LINN.)- 

 BLACK-THROATED LOON. 



Urinator arcticus (Linn.), A. O. U. Check List, 1895, p. 4. 



Distr. : Northern part of the northern hemisphere ; south in winter 

 to the northern United States, east of the Rocky mountains. 



Adult in summer: Top of head and nape, gray; throat, black; 

 upper plumage, black, glossed with purplish reflections; sides of neck 

 with longitudinal white streaks; rest of under parts, white. 



Adult in winter, and immature: Upper parts, blackish, many 

 feathers with grayish edgings; throat and under parts, white. 



Length, about 27; wing, 11.50 to 13.15; bill, 2.55 to 2.80; depth 

 of bill at base, about .78. 



The Black-throated Loon is a boreal species which occasionally, 

 but rarely, occurs on Lake Michigan in late fall and winter. 



"A very rare winter visitant on Lake Michigan." (Nelson, Birds 

 N. E. Illinois, 1876, p. 150.) "This is certainly a very rare bird 

 in Wisconsin, occurring only as a straggler in late fall or winter. 

 We have access to but three unquestionable records." (Kumlien 

 and Hollister, Birds of Wisconsin, 1903, p. 7.) "Exceedingly rare; 

 Lake Michigan; winter." (A. J. Cook, Birds of Michigan, 1893, p. 30.) 



9. Gavia stellata (PONTOPPIDAN). 

 RED-THROATED LOON. 



Urinator lumme (Gunn. ), A. O. U. Check List, 1895, p. 4. 



Distr.: Northern North America, breeding north of the United 

 States, south in winter occasionally as far as the Gulf of Mexico. 



Adult in summer: Back, fuscous, spotted with white; throat and 

 fore neck, plumbeous gray ; middle of fore neck with a patch of rich 

 chestnut; back of neck, black, streaked with white; rest of neck and 

 head, plumbeous gray; breast and belly, white. 



Adult in winter, and immature: Similar to the winter plumage of 

 the Black-throated Loon, but the back is spotted with white; fore 

 neck and throat, white or grayish white, without chestnut. 



Length, 25; wing, 10.50 to 11.50; bill, 2.30; tarsus, 2.75 



While this species varies greatly in size, and size and shape of the 

 bill, it is never as large as G. immer, and may be distinguished from 

 G. arctica in the adult by the chestnut red throat and in the immature 

 birds by the white spotting of the upper parts. These spots are most 

 numerous in the upper back and wing coverts and less numerous 

 but larger on the scapulars and tertials. On the middle of the back 

 they are comparatively few and scattered, sometimes almost wanting. 



