V ° l 'wi9 XVI ] Bent, Variation in the Black-throated Loons. 241 



Gavia arctica viridigularis (Dwight) 



4 males from Bering Sea region, 

 average, bill 2.63 wing 12.69 

 largest, " 2.87 " 13. 

 smallest, " 2.50 " 12. 



The other characters are equally confusing. The nape is lightest 

 and almost constantly so in North American pacifica; it is darkest 

 in viridigularis and more or less intermediate in many specimens 

 of the other two forms. 



The black throat patch terminates below in a straight line almost 

 invariably in North American pacifica; I have seen but one excep- 

 tion to this rule; but in Siberian pacifica this character is less 

 constant. In viridigularis this patch terminates below in a decided 

 point, in all specimens that I have seen. In European arctica 

 about half of the specimens I have seen have the patch decidedly 

 pointed below and the others have it nearly straight or only slightly 

 pointed. 



The colored reflections of the black throat-patch are the most 

 variable and inconstant of all the characters. In viridigularis 

 three of the specimens examined show mainly greenish colors but 

 even these show some signs of purple; and in one, a bird in my own 

 collection, the colors are about equally divided. In European 

 arctica about half of the specimens show mainly purplish reflections, 

 while fully half show both purplish and greenish. In North Ameri- 

 can pacifica the purplish reflections predominate, but five speci- 

 mens out of twenty-two show more or less greenish in certain lights. 

 Mr. Waldron DeWitt Miller, in sending me descriptions of Pacific 

 Loons in the American Museum, used the following terms in desig- 

 nating the colors of the throats; greenish-blue, bluish-green, dark 

 greenish-blue, violaceous and dark violet. It can be easily seen 

 from the above that the colors are very variable. 



Dr. Dwight says, in his diagnosis of viridigularis: — "The green 

 coloration of the throat is the essential character that sets this 

 species apart from arctica and its races, which all have purple 

 throats." In the light of the facts stated above this "essential 

 character" disappears and his new species must be reduced to the 



