^'°'- '^- I HUTTON, Land Birds of New Zealand. Q? 



1905 J ' ' '' / 



But if we cannot claim these variations as due to the action of 

 environment, neither can we claim them for natural selection. 

 We can understand how natural selection may have strengthened 

 the bill in Turnagra and elongated it in Heteralocha, but I can 

 see no reason for believing that it has had a hand in bringing 

 about any of the specific changes that I have mentioned. For 

 natural selection can only affect changes that are useful to the 

 animal, and it is impossible to think that the changes in plumage, 

 or in the colour of the wattles, can have had any selective value. 

 Most of the cases are evidently connected in some way with 

 isolation, but there are exceptions as in Sphcnczacus, Rhipidura, 

 Ocydromus, and Apteryx. 



The case of Ocydromus is especially interesting. Here we find 

 0. earli in the North Island and in Stewart Island, but not 

 in the South Island, which lies between them. Or if it occurs 

 in the South Island it is so rare that I have never seen a specimen 

 from there. In the South Island we have four other species, 

 each of which is fairly well confined to a distinct habitat. O. 

 australis inhabits the low lands all round the island ; O. hectori 

 is found on the hills, 0. brachypterus in the West Coast sounds, 

 and 0. finschi in the neighbourhood of Lake Te Anau. O. aus- 

 tralis is also found in Stewart Island, where it appears to inter- 

 breed with O. earli, if we may judge from the number of 

 individuals that come from there which are intermediate in 

 plumage between the two. And although hybrids are very rare 

 in a natural state, I am inclined to think that O. finschi is a 

 hybrid between 0. brachypterus and 0. australis. 



Now, the only explanation of these phenomena appears to me 

 to be the supposition that at one time 0. earli spread over all 

 three islands ; that it remained unaltered in the North Island, 

 while in the South it gave rise to 0. australis and O. brachypterus 

 and then disappeared ; 0. hectori being afterwards derived froi^ 

 O. australis. But why these differences should have arisen I 

 cannot surmise. 



Another very interesting case is Cyanorhamphus erythrotis, 

 which occurs at the Antipodes and at Macquarie Island. It 

 differs from C. novcB-zealandice by its yellow tint. It is extremely 

 improbable that the Parrakeets of Macquarie Island came from 

 Antipodes, or vice versa. The islands are further apart than 

 either of them is from New Zealand ; and both Campbell and 

 Auckland Islands, on which the species is not found, lie close 

 to the track. On the other hand C. novce-zealandicB is often 

 affected by xanthochroism, due to the imperfection of the 

 feathers, and is therefore tinted more or less with yellow. I 

 have seen a specimen from Southland of a bright canary-yellow. 

 From Antipodes Island I have also seen a yellow variety of C. 

 erythrotis, which on being kept in confinement turned green, 

 owing, no doubt, to the large supply of food inducing the green- 

 making superstructure of the feathers to be developed. 



Now it seems probable that C. erythrotis originated inde- 



