12 HAWAIIAN BIRDS. 



can hardly be held to be at the commencement of its existence 

 as a separate race, but, on the contrary, must be held to have 

 reached its present stage of distinctness only after a very long 

 period of time. It would seem to be much more probable that 

 a bird so completely dififerentiated, if weak in numbers and oc- 

 cupying but a small area, is nearing the final stages of its career 

 than that the species is in its incipiency. 



The rarity and extreme degree of localization of such birds as 

 Viridionia are the more remarkable and the more, difficult to ex- 

 plain, unless upon some such theory as inbreeding, inasmuch 

 as the environment of the bird up to within two or three years 

 (its home is now being invaded by the axe) appears to have 

 been peculiarly favorable, and is evidently markedly so for other 

 Drepanine forms, such as Heterorhynchus, Chlorodrepanis, Ore- 

 omyza and Loxops, as is evidenced by their numbers. 



In respect to its small numbers and the limited extent of 

 country occupied, Viridonia is, perhaps, an extreme case among 

 Hawaiian birds, but there are others scarcely less remarkable. 

 Pseudonestor and Palmeria of Maui, and Chloridops and Rhoda- 

 canthis of Hawaii are closely parallel, though not so extreme, 

 cases. These birds, except Palmeria, which occurs also on Molo- 

 kai, are confined to single islands and to a comparatively small 

 part thereof. 



If inbreeding be accepted as a true and sufficient cause of the 

 present insecure footing of Viridonia under environmental con- 

 ditions of its own choosing, the same theory seems applicable 

 in the case of the other species. 



To the same list may also be added the extinct, or nearly 

 extinct, Ciridops, and the extinct Meliphagine form Chcetoptila. 

 None of the above birds appear to have suffered from enforced 

 conditions or external agencies, except as regards compulsory in- 

 breeding. 



The two latter species, indeed, were both extinct, or practi- 

 cally so, long before their forest haunts had been interfered with 

 by man in the slightest degree. Whether or not inbreeding 

 played any part in the tragedy, their extinction must, at any 

 rate, be assumed to be due to what may be termed natural 



