322 BULLETIN OF THE 



imply a diversity of species ; they only accord with what would naturally 

 be expected to occur if A. mexicanus and A Cooperi were known to con- 

 stitute but a single species.* 



Accip'tter Cooperi, as is well known, is not only closely allied in general 

 structure to Buteo lincatus, but also in style of coloration in both the imma- 

 ture and adult stages. It may be fair, then, to test the value of the dis- 

 tinctive characters assigned to A. mexicanus by what obtains as geographi- 

 cal variations in size and color in Buteo linealus Of this species I have 

 fortunately a large number of specimens, including some from localities 

 similarly separated to those whence A. Cooperi and A. mexicanus respec- 

 tively come. In the case of Buteo linealus there is no reason whatever to 

 doubt that my specimens from Florida and New England are specifically 

 identical. Yet the Florida specimens are very much brighter colored, and 

 very much smaller ; the difference in the length of the folded wing between 

 two males, one of which is from Maine and the other from Florida, being 

 two and one half incites, with corresponding differences in general measure- 

 ments. This is relatively much greater than the difference in size between 

 specimens of the so-called A. Cooperi and A. mexicanus. Similar varia- 

 tions in color and size to those between A. Cooperi and A. mexicanus also 

 occur between northeastern and southwestern specimens of A.fuscus, the 

 latter, as already noted under A. fuscus, being smaller than the former, 

 and very much brighter colored ; the difference in color between speci- 

 mens from Maine and (he State of Missouri being greater than is repre- 

 sented to occur between A. Cooperi and A. mexicanus, and of a parallel 

 kind. In accordance with the evident inference that may be drawn from 

 these facts, I provisionally include A. mexicanus among the synonymes of 

 A. Cooperi. The A. Gundlachi of Cuba differs from the southern A. Coop- 

 eri in the way southern birds usually differ from the northern ones of the 

 same species,, that is, in being smaller and brighter colored, and in having 

 the dark transverse bars on the under plumage increased in breadth at the 

 expense of the alternating light ones. 



86.* Buteo borealis Bonaparte. Red-tailed Hawk. 



Falco borealis Gmelin, Syst. Nat., I, 266, 178S. — Wilson, Am. On., VI, 

 75, pi. lii, fig. 2, 1812.— Rich. & Swain., Faun. Bor. Am. II, 50, 1831.— 

 Audubon, Om..Biog., I, 265, pi. II, 1832. 



Buteo borealis Bonaparte, Geog. and Comp. List, 3, 1838. — Gossi, Birds 

 of Jamaica, II, 1847. — Lemiseye, Av.dc la Isla dc Cuba, 18,1850.— 

 Cassin, Syn. N. A. Birds (Illust. Birds Cal. and Texas, etc.), 97, IS34.— 

 Brewer, N. Am. Oology, 21, 1857. — Cassin, Baird's Birds of N. Am., 

 25, 1858. — Bryant, Proc. Bost. Soc. Nat. Hist., VIII, 109, 1861.-- 

 Allen, Memoirs Bost. Soc. Nat. Hist., I, 499, 1868. 



* Bonaparte indeed long since cited A. mexicanus Swainson as a synonyme of A. 

 Cooperi. 



