306 



NORTH AMERICAN BIRDS. 



parative Zoology, Cambridge, 10 ; Cab. Gr. N. Lawrence, 6 ; Coll. W. S. Brewer, 3 ; R. 

 Ridgway, 4. Total, 85. 



Measurements. 



That all the North American Eough-legged Hawks, whether light or dark 

 (excepting of course the A. ferruginous), are one species, and also one race, 

 there appears to be but little doubt ; a critical comparison and minute ex- 

 amination of about one hundred specimens also proves that the dark plu- 

 mage, usually separated as " A. sancti-johannis," has nothing to do with age, 

 sex, season, or locality, but that, as in Buteo borealis var. calurus and B. 

 swainsoni, it is a purely individual condition, black birds being black, and 

 light birds being light, from the first plumage till death. Each phase has its 

 young and adult stages distinctly marked, as the above diagnoses point out. 

 It however appears to be the fact that certain regions are frequented more 

 by birds of one color than another, and of the many hundreds of specimens 

 sent from the Arctic regions to the Smithsonian Institution by officers of the 

 Hudson's Bay Company, none exhibited the blackish plumage which, on the 

 other hand, appears most abundant about Hudson's Bay. 



The North American birds are distinguishable from European ones (var. 

 lagopus) by the characters given in the synopsis on p. 1619, and description, 

 on p. 1624 



Habits. The Eough-legged Hawk of North America bears so close a 

 resemblance to the European species, in all respects, — plumage, habits, and 

 eggs, — that the two are generally considered to be identical. The distribu- 

 tion of the American variety appears to be nearly throughout, the entire 

 Union, from the Atlantic to the coast of the Pacific, and from New Mexico 

 to the Arctic regions. It was taken at Fort Steilacoom, and at Shoal-water 

 Bay in Washington Territory, by Drs. Suckley and Cooper. It was not seen 

 by Mr. Dresser in Texas nor by Dr. Woodhouse in New Mexico, but it was 

 taken near Zuni by Dr. Kennerly, was found from Mimbres to the Eio 

 Grande by Dr. Henry, and obtained near Fort Fillmore by Captain Pope, 

 and at Fort Massachusetts by Dr. Peters. 



The Eough-legged Hawk is quite abundant in spring and fall in the 

 neighborhood of Niauara Falls. In the fall of 1872, Mr. James Booth met 

 with a pair of this species, accompanied by their young. The latter were 

 fully grown. The male bird was in very black plumage, while the female 

 was unusually light, the pair thus presenting well-marked illustrations of 

 the two types, the black sancti-johannis and the common lagopus. The 

 parents were secured, and are now in the museum of the Boston Society of 

 Natural History. One of the young was also shot, but I did not see it. 



