34 



LIST OF DIURNAL BIEDS OF PREY. 



Norwich Museum, thi'ougb the good offices of Mr. E. P. Ramsay ; they have none of them 

 been sexed by the collector, but are all larger than the two immature males from the 

 neighbouring island of San Christoval, of which I have given the dimensions in the ' Ibis' 

 for 1881, p. 261, and for 1882, p. ISO. The five Ugi specimens measui-e as under : — 



Wing. 



inches. 

 Immature, with some down still attached ... 8'75 



Ditto, with no down remaining 9'40 



White-breasted adult lOO 



Ditto, ditto 10-0 



Melanistic adult O'SO 



The last-named specimen is an example of the black hawk for whicli Mr. Ramsay, 

 in the first instance, proposed the specific name '^ versicolor,^' but which he subse- 

 quently considered not to be separable from U. albigularis. I concur in the latter 

 view, and think it probable that it is a melanistic phase, possibly hereditary, of the 

 white-breasted bird; such melanisms, as is well known, occur in other raptorial birds, 

 of which I may mention two very similar instances on the African continent, Accipifer 

 onelmioleucus and Butco cmgur. The specimen now referred to is a slaty black on the 

 exposed portions of the feathers, but the basal moieties of the primaries are white on 

 the inner webs, cross-barred and freckled with dark slate-colour, and the under surface 

 of the tail is indistinctly crossed with dark brown bars on a ground of somewhat 

 lighter brown ; in both these particulars it resembles the white-breasted adults, except 

 that in these the barring on the under surface of the rectrices is less indistinct. The 

 two immature specimens are evidently younger than that figured in the 'Ibis' for 1881 ; 

 they resemble it on tiie upper surface, but differ in having a blackish-brown shaft-mark 

 on each feather of the throat, and in the ground-colour being of a much darker and 

 richer rufous on all the underparts, including the wing-linings, and in all these parts 

 being broadly and regularly cross-barred with blackish brown. 



