WHITE-TAILED HAWE. 277 
two, the differential characters are of more importance and 
utility than the most laboured descriptions. 
This comparison we have carefully instituted between our 
American specimens and others from Africa and Java. They 
agreed perfectly, especially with that from Java, in every, the 
minutest character, even feather by feather, much better than 
birds of prey of the same species and from the same country 
do generally. They are even more alike than different speci- 
mens from the old continent of the black-winged itself, since 
that species is said to vary considerably in the black markings, 
which extend more or less on the wings in different individuals. 
Nevertheless, a constant, though trivial, differential character, 
added to the difference of locality, has induced us to follow 
Temminck’s course, in which we should never have ventured 
to take the lead. ‘This character consists in the tail being in 
Falco dispar constantly irregular, while in F. melanopterus 
it is even ; or, to explain it more clearly, the outer tail-feather 
is rather the longest in the African, and more than half an 
inch shorter than the next in the American species. his 
essential character is much more conspicuous in Temminck’s 
plate than in ours, owing to the tail being spread. In the 
black-winged, also, the lower wing-coverts are destitute of the 
black patch so conspicuous in the American bird ; a female 
from Java has, however, a slight indication of it, but no trace 
of it is observable in our African males. 
By admitting this to be a distinct species from the black- 
winged hawk, we reject one more of those supposed instances, 
always rare, and daily diminishing upon more critical obser- 
vation, of a common habitation of the same bird in the warm 
parts of both continents, without an extensive range also to 
the north. A steady and long-protracted exertion of its 
powerful wings would have been requisite to enable it to pass 
the vast and trackless sea which lies between the western coast 
of Africa, the native country of the black-winged hawk, and 
the eastern shores of South America. Yet, were the species 
identical, this adventurous journey must have been performed. 
