MUSEUM OF COMPARATIVE ZOOLOGY. 321 



one Interested in geographical color variations in animals; the more so, 

 perhaps, from the two latter species being so intimately related as to have 

 been at one time generally regarded as identical. Yet so far as can be 

 judged from a limited number of specimens, Astur palumbarius differs 

 more from A. alricapillus than Accipiter nisus does from Accipiter fuscus, 

 which latter species have never been considered as identical.* 



85.* Accipiter Cooperi Cassin. Cooper's Hawk. 



Falco Cooperi Boxap., Am. Orn., II, 1, 1828. 



Falco Stanlei/i Aldlbon, Orn. Biog., I, 186, 1831 (young). 



Astur Cooperi Bonap., Geog. and Comp. List, 5, 1838. 



Accipiter Cooperi Cassin, Must. Birds of Cal., etc., 96, 1854. 



Accipiter mericanus Swain., Faun. Bor. Am., II, 45, 1831. — Cassin, Baud's 



Birds N. Am, 17, 1858. 

 Accipiter Gundlaclu Lawk., Ann. N. Y. Lye. Nat. Hist., VII, 252, 1860. 



Common. 



Mr. Cassin has very properly indicated the variations in sice and color 

 commonly seen in this species in the following remarks: " Rather a diffi- 

 cult species to the ornithologists, on account of the great variations in its 

 colors, and in size also. It is, in fact, unusual to find two alike in a dozen 

 specimens." t Its relationship to Accipiter Juscus is of course well under- 

 stood, it holding a similar relationship to that species that Picus villosus 

 does to Picus pubescens, the essential difference between them being mainly 

 a great difference in size. But the specific distinctness of A. mexicanus 

 from it is not so clear. Being without authentic specimens of A. mexi- 

 canus, and having only New England specimens of A. Cooperi,% I cannot 

 speak confidently respecting the character and affinities of the former. 

 According to authors, however, it seems to differ from A. Cooperi in being 

 somewhat smaller and more highly colored. It is also more southern in 

 its distribution. Hence these variations, being in accordance with the 

 general laws of geographical variation in size and color, do not necessarily 



* In this connection I wish to cite some interesting variations in color presented by 

 Massachusetts and Maine specimens of Astur alricapillus. Ordinarily this species has 

 each feather below centred with a longitudinal dark shaft-line, with several transverse 

 broader but somewhat irregular dark ashy-brown bars on a lighter ground. Some 

 specimens, however, as one from Maine, have the transverse bars so narrow and 

 broken that the lower surface presents a nearly uniform, minutely mottled appear- 

 ance. Another specimen (from Springfield, Muss.) represents the opposite ex- 

 treme, it having the transverse bars broad, regular, and quite far apart, so that its 

 resemblance to average specimens of Astur palumbarius is very close. The color in 

 this specimen is much darker throughout than is usual in this species. 



t Illustrations of Birds of California, etc., p. 93, 1854. 



| Since the above was written, specimens have been received at the Museum from 

 Jalapa, Mexico, from Sn. E. Montes-de-Oca. 



