Vol. xx.-| Mathews, Nature of Neiv Zealand Avifauna. 2IQ 



1 92 1 J ' -^ 



items used for comparison. Tliey. are certainly not nearly 

 related to the Pittas. 



The birds locally known as Tomtits and Robins are relations of 

 the Australian Pdroica'XxkQ birds, and appear to have arrived in 

 New Zealand probably about the same time as the antecedents of 

 the Petroica series invaded Austraha. Isolation caused their 

 evolution in different directions, and thus we get the Robin {Miro 

 amtralis) as a large form, while the Tomtits {Myiomoira macro- 

 cephala and toitoi), perhaps through competition, as degenerate 

 species. An interesting item are the two Black Robins {Nesomiro 

 traversi and dannefcerdi), which appear to have evolved inde- 

 pendently on similar lines in achieving an entire black plumage 

 on far distant isolated islands. We here suggest that they have 

 developed from a form of Myiomoira, and not from Miro, with 

 which they were associated until we separated them. 



Another Austrahan form, the Fly-eater, is represented by a 

 species which is a little different in structure as well as in habits. 

 In order to emphasize these differences we have called the main- 

 land New Zealand form Maorigerygone, while the Chatham Islands 

 species had been distinguished previously as Hapolorhynchits, on 

 account of its extraordinary large size and pecuhar bill — a 

 beautiful example of evolution by isolation on islands. A note- 

 worthy item is the retention of aboriginal coloration, while 

 structural changes are manifest and of great import. 



The New Zealand Fantails, Rhipidura flabellifera and fnliginosa, 

 are as interesting as any birds could be, as it is obvious they are 

 only recently immigrants from the mainland, and, while the 

 species was spreading throughout AustraUa without a great deal 

 of variation, a melanistic " sport " was -produced in the south 

 of New Zealand, and this melanism is now spreading over the 

 islands and probably displacing the original form. We do not 

 know of any similar case of melanistic displacement in progress, 

 but these forms show how such may occur. At the present time 

 the two birds breed together without producing hybrids, each 

 form appearing quite distinct from the egg upwards. 



The Thrushes of New Zealand constitute an endemic family 

 whose exact relations are unknown, and the name " Thrush '' is 

 only used as they are superficially large Thrush-sized birds with 

 an obscurely spotted breast. 



The Fern-Birds {Boivdleria) are, again, endemic and of family 

 rank, their aUies certainly not being the South African Sphenccacus, 

 with which they were confused many years ago. They are island 

 modifications of some such form as that from which the Aus- 

 tralian Atrichornis was derived. 



To the family ParidcB three very different species are allotted 

 simply because a new family for each seems too much to admit 

 at present ; but they have as httle real affinity with the Palaearctic 

 Tits as the Australian Whitefaces (Aphelocephala) have. 



The Yellow-head {Mohoiia ochrocephala) may be distantly 

 related to the White-head {Certhipariis alhiciUa), but whether 



