INTERESTING PROBLEMS CONCERNING THE AVIFAUNA 353 



are represented by different species in some of the ont-lying 

 islands. Some badly-flying species, such as the fern-bird, the 

 warblers, the f antails, and the wrens, are identical on both islands 

 of New Zealand. Some of the rails remain unchanged, while 

 others have varied greatly. While the fern-birds, the tits, the 

 warblers, and the fantails have undergone only specitic changes 

 since their ancestors came to New Zealand, the New Zealand 

 members of the creepers (Paridte) and of the honey-suckers have 

 changed considerably. Enough has been said to show that not 

 only do different species vary at different rates, but that the same 

 species varies at different rates in different places. 



New Zealand is well placed for studying the effects of environ- 

 ment on variation, but the study lands the investigator in puzzles. 

 Certainly there is greater variety of conditions in the South 

 Island than in the North Island, and the South Island has a 

 larger number of species, but it seems to be impossible to connect 

 the difference of conditions with any of the specific changes. 

 Why should the crow have an orange wattle in the South Island 1 

 Why should the wood-hens be darker in the neighbourhood of the 

 West Coast Sounds, and lighter in the sub-alpine ranges? Why 

 should the fern-bird get paler in the south? Wliat has the 

 fawn-coloured breast of the rock-wren to do with living among 

 rocks '? 



A special example may be taken. The green parrakeets, 

 although not confined to New Zealand, have their headquarters 

 here. There are three species living together in the South Island, 

 two on the Antipodes, two on the Auckland Islands, and one each 

 on the Chatham Islands, and Macquarie Island. The Auckland 

 Island birds have not varied in plumage from the original stock 

 in New Zealand, although they must have been isolated for a long 

 time, as the crest of the breast-bone has undergone a reduction in 

 size. The Antipodes Island parrakeet has varied considerably^ 

 but the Chatham Island and the yellowish parrakeet slightly; 

 and it is impossible to connect these changes with the surrounding 

 physical conditions. 



If we cannot claim these variations as due to the action of the 

 environment, neither can we claim them for natural selection. 



