Plumages o/Buteo solitarius. 391 
it would be contrary to the general law in American Hawks, 
in which, if I am not mistaken, the barring is better defined 
and more constant in the adult stage. In the series of 
specimens in the dark phase, however, the barring of the tail 
is seen to be more of an individual character. In most, 
though not all, of the adults the barring is well defined. 
So it is also in most of the juveniles, but in one, the 
youngest, perhaps, of the series, it is scarcely indicated 
at all, and the same remark holds good of two individuals in 
an intermediate stage. 
It is perhaps idle to speculate as to the origin and 
significance of these two very difi'erent phases of plumage. 
As, however, the dark phase so largely predominates, at 
least on the rainy and windward side of the island, it has 
occurred to the writer that the progenitors of this Hawk, 
when they first came to the island, may have been light- 
coloured ; and that now, after a long residence, the bird 
is in process of undergoing transformation into an almost 
black form. 
In this connexion it is noticeable that white is almost 
entirely absent from Hawaiian birds, the majority of which 
incline strongly towards greens and yellows, with a minority 
which are clad in red and black. Chasiempis alone of the 
woodland birds exhibits much white in its plumage, and 
even this bird has less white and is of a deeper and more 
lustrous brown in the rainy regions of Hawaii than in the 
drier districts, there being, indeed, two forms or colour- 
varieties *. 
The feathering of most of the island forms, especially of the 
J)repanidid(2, which form the bulk of the indigenous birds 
both in individuals and species, is exceedingly abundant and 
compact, and is possessed of deep and lustrous tints, all 
of which are indicative of a cool and rainy climate, that 
necessitates a warm covering and confers a rich, though by 
no means necessarily bright or gaudy, coloration. 
It is to be remembered in this connexion, however, that 
there are at least two American Hawks, Buteo swainsoni and 
* A discussion in detail of these colour-varieties will be found in a 
paper by the author in a recent issue of ' The Auk.' 
