390 Mr. H. W. Ilcnsliaw on the various 



under wing-coverts faintly ferruginous, with blackish spots 

 and streaks ; under parts blackish, the feathers on the thighs 

 and tibise 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 feather barred or streaked with blackish 

 brown, which is the prevailing colour on the sides of the 

 neck, flanks, and tibise. 



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 



