9 8 HUTTON, Land Birds of New Zealand. [5th"jan 



pendently in Antipodes and Macquarie Islands, from different 

 flocks of C. }iovce-zcalandice from New Zealand. It is probable 

 that the small number of individuals on each of the islands 

 allowed the xanthochroism to obtain a permanent influence, 

 which it could not do in New Zealand, on account of the large 

 number of birds and the greater facilities for intercrossing. Thus 

 we have a new species produced by the isolation of a few indivi- 

 duals. And we also have a case of the double origin of the same 

 species. This last cannot occur often ; but it shows that the 

 great difterences between the climates and vegetation of Antipodes 

 and Macquarie Islands failed to produce any eftect. 



Another curious case is the interbreeding of two species of 

 Fantails. That they are distinct species is proved by the fact 

 that Rhipidura fiabcllifera is common in both islands, while 

 R. fuliginosa is confined to the South Island. In the latter 

 place an individual of one species is commonly seen courting one 

 of the other species. But the most remarkable circumstance is 

 that the young in these union nests never show their origin by 

 their plumage. They are either R. fiabeUifera or else R. fuli- 

 ginosa. Sometimes all are R. fiabeUifera, sometimes they are 

 mixed ; but R. fiabeUifera is generally the more numerous in 

 a nest. 



Again, New Zealand ornithologists have special advantages for 

 studying the eftects of the absence of enemies on development, 

 the most important of which is degeneration in the powers of 

 flight. Indeed, no part of the world ofters so many examples of 

 degeneration in the wings of birds as does New Zealand. There 

 are strong-flying birds, such as Nesierax novce-zealandioi , Nestor 

 notabilis, the Parrakeets, and Ducks ; as well as a chain of more 

 or less degenerate birds, passing through ProstJiemadera, Turn- 

 agra, Glaucopis, HeteralocJia, and Spfienaacus to Stringops, 

 Ocydronius, Nesonetta, and Apteryx, which cannot fly at all. 

 And in these non-flying birds there are some with large wings, 

 like Stringops ; others with small wings, such as Ocydronius and 

 Apteryx ; and none at all in the extinct DinornitJiidce, in most 

 of which even the shoulder-girdle had disappeared. 



In some of the outlying islands the Snipes, Larks, and Parra- 

 keets are but feeble flyers, although their relations in New 

 Zealand fly well. So general an eftect upon birds of so many 

 difterent kinds must be due to some general cause, and we find 

 it in the baneful effects of the want of competition. 



The fact that on some of the outlying islands we find several 

 birds with feebler powers of flight than their congeners in New 

 Zealand, although they have no more enemies in New Zealand 

 than on the islands, is very remarkable. We may accept natural 

 selection as the cause of loss of powers of flight when that loss 

 has been useful to the species ; as in the case of Parrakeets and 

 Larks on small islands much exposed to gales of wind, as the 

 Antipodes. But this will not apply to the Ducks of the Auckland 

 Islands, or to any of the birds on the main islands of New Zealand. 



