HAWAIIAN BIRDS. 83 



preserve the species from extinction, laws should be passed pro- 

 tecting this hawk and imposing a heavy penalty for its destruction. 



Like its American relatives of the genus Buteo, io is fond of 

 soaring high in air in fine weather, especially towards midday, and 

 once above the forest trees the bird mounts upward in wide 

 spirals without perceptible movement of the wings until he is 

 almost lost to sight in the blue ether. Urider ordinary circum- 

 stances the flight of this hawk is heavy and labored, and is main- 

 tained at first by a series of rapid-wing-beats until the bird has 

 secured good headway. 



An instance has recently come to my notice where a hawk, un- 

 doubtedly of this species, accompanied a vessel all the way to Cal- 

 ifornia, most of the time perched on the royal yards. From this 

 lofty perch, whence it could survey the ocean for miles around, it 

 occasionally sallied forth after food which consisted of small 

 birds, doubtless petrels. 



The plumages of this hawk have not been well understood.* 

 There is an extraordinary amount of individual variation, and in 

 a series of over twenty specimens no two are alike. There are, 

 however, but two distinct types or phases of the adult plumage, 

 a very dark phase, in which the bird at a short distance appears 

 to be black, and a light phase, in which the bird seems to 

 be almost white. The juvenile plumage of each of these phases 

 is very distinct from each other and from the corresponding adult 

 condition; both of them, however, I believe have been described 

 by authors as adult plumages. Juvenile specimens in the dark 

 phase are very dark brown, but by no means so dark as the adult ; 

 those of the light phase are of a light brown type. Juveniles of 

 both phases are, I think, several years in acquiring the adult 

 plumage. The brown stripes and bars underneath are gradually 

 replaced with buff in the light phase, and in the dark phase deepen 

 and finally overspread the entire under surface. 



The light and dark phases appear to mate in every possible 

 combination, pairs of dark birds, pairs of white birds, pairs with 

 both phases represented. 



Dark birds are very much more numerous, at least on the wind- 



*For a paper upon this subject by the author see "Ibis" for igo2. 



