390 Mr, H. W. Henshaw on the various 
under wing-coverts faintly ferruginous, with blackish spots 
and streaks ; under parts blackish, the feathers on the thighs 
and tibiae having a ferruginous wash. 
Juvenile stage. — Above dark chocolate-brown, darkest 
on the upper back ; feathers of the occiput and hind-neck 
lightly bordered with ochraceous; tail lighter brown, each 
feather barred with black or with bars indicated ; below 
rusty buff, each featlier barred or streaked with blackish 
brown, which is the prevailing colour on the sides of the 
neck_, flanks, and tibiae. 
A series of eleven specimens sufficiently well illustrate 
the changes from the juvenile phase to the fully adult. The 
latter is practically black. 
As the juvenile bird approaches the adult state it gradually 
doffs the rusty tinge above and below, which is the charac- 
teristic feature of the immature bird, and becomes blacker 
and blacker. The writer has recently seen a living individual 
in the dark phase but a few months old, and its appearance 
indicates that a bird must be three or four years old before 
reaching the final adult plumage. 
Buteo solitarius inhabits both the dry and the rainy side 
of Hawaii. On the rainy side the dark phase largely pre- 
dominates, at least 75 per cent, of the Hawks belonging 
to it. The author is at present unable to state whether 
or not the light-coloured phase is more abundant in the dry 
region than it is in the wet. Judging by analogy this should 
be the case. 
In this species, the presence or absence of black barrings 
on the tail and their comparative degree of intensity seems to 
be largely individual attributes, and to be fully indicative 
neither of age nor of sex. It is true that in the series 
of twelve specimens in the white phase the bars are present 
and well marked in all the juveniles, and there seems to be 
. a progressive loss of these bars as the adult state is reached. 
They are indicated in all the adults, and are better defined 
on the outer rectrices than on the inner, being almost 
obliterated on the middle pair ; but in none of the adults 
are they so well defined as in the juveniles. 
If this could be shown to be the rule in the present species 
