NO. 1195. BIRDS FROM CENTRAL ASIA— OBEBHOLSER. 217 



There seem to be, however, four principal phases: One in which the 

 lower parts are very light colored, with little or no rufous, and with 

 comparatively inconspicuous streaking; another, in which the under 

 surface has more rufous, is much streaked anteriorly aud barred or 

 mottled posteriorly; a third, in which the entire lower surface is almost 

 without obvious streakings, being rufous on throat and breast aud dull 

 brown on the hinder portions ; and a fourth, in which the whole x)lumage 

 above and below is almost uniform sooty brown. Connecting these sev- 

 eral places there exists an almost unbroken series of intermediates. 

 Doctor Sharpe considers that the last-mentioned condition is the very 

 old bird,' and that each individual is very light when young, gradually 

 darkening with advancing years. The present series of specimens 

 offers much to corroborate this theory, and very little, if indeed any- 

 thing, to oppose. The birds in the first of the above-mentioned phases, 

 are without any doubt very young, and. those of the last two are just 

 as unquestionably adults. Those uf the second phase are not so satis- 

 factorily determinable, but they seem to be in a transition state, although 

 how many years are required to assume this plumage must still, of 

 course, be a matter of conjecture. Were any of the darkest specimens 

 young birds they would easily establish a case of dimorphism very 

 similar to that of the American Buteo swainsoni, to which, in its various 

 phases of plumage, the present species bears no slight resemblance. 

 Without such examples, however, it seems premature to advance this 

 hypothesis as more than a suggestion, and in the light of our present 

 knowledge we must regard the various differences of plumage as the 

 result of age. Only one individual of this series has a completely red 

 tail, though several have a greater or less tinge of rufous. The old 

 adults, as also the very young birds, appear not to have a rufous tail; 

 so that unless we are in error as to the sequence of plumage, the rufous 

 tail belongs, rather curiously, to a transition stage. 



In some conditions of plumage the present species is very difficult 

 to distinguish from Buteo desertoricm, but the larger size of the former 

 will usually serve for identification. 



ACCIPITER NISUS (Linnaeus). 



Falco nisiis LiNNiEUS, Syst. Nat., lOtli ed., I, 1758, p. 92. 

 Accipiter 7tisiis Pallas, Zoogr. Eosso-As., I, 1826, p. 370. 



Two examples. One is an adult male from Sind Valley, Cashmere, 

 at 6,000 feet altitude, taken December 14, 1895: "Iris and feet yellow; 

 claws black ; bill black, the base horny blue. Length, 1 3^ inches." The 

 other is an immature female from Srinagar, Cashmere, December 30, 

 1895: "Iris yellow; bill black, horny blue at base; cere yellowish green ; 

 feet yellow with a tinge of green on tarsus; claws black. Length, 15^ 

 inches. Stomach contained the remains of small birds. This hawk was 

 pursuing a jackdaw when shot." 



' Cat. Birds Brit. Mas., I, 1874, p. 177. 



