INTERESTING PROBLEMS CONCERNING THE AVIFAUNA 351 



The ancestors of the present species may have crossed the Tasman 

 Sea, and so have come to New Zealand from the west; or the 

 rehitionship may be due to two branches of emigrants from New 

 Guinea going southwards, one of which passed into Australia, 

 and the other into New Zealand. In this category we have the 

 warblers, the tits, the wood-robins, the creepers, the fantails, 

 the honey-suckers, the ground-lark, the kingfisher, the parrakeets, 

 the morepork, the quail-hawk, as well as several rails and ducks. 

 Some of these may have crossed the Tasman Sea, but it is more 

 probable that the ancestors of most of them came to New Zealand 

 from New Caledonia. 



There is good reason for thinking that a migration of land- 

 birds into New Zealand from the north took place in the Eocene 

 Period, for it is highly improliable that New Zealand was ever 

 again connected with the mainland. In the two following Periods 

 New Zealand stood at a lower level than at present by some 3,000 

 feet, but in the older Pliocene it had a much greater extent, and 

 included the Chatham Islands, which were again separated from 

 New Zealand in the newer Pliocene. If we knew in detail the 

 history of the origin of the land-birds of New Zealand, it would 

 enable us to solve several interesting problems in the development 

 of species, or, at any rate, would throw considerable light upon 

 them ; but as that is impossible, we must do the best we can with 

 the imperfect knowledge we have. 



In the first place, we learn something about the relative ages 

 of certain groups. For all those groups which are fairly well 

 represented in the fauna, such as the parrots, the rails, the 

 herons, the plovers, the ducks, and the kiwis, are, in all proba- 

 bility, old groups, unless they have crossed the Tasman Sea. The 

 perching birds are also well represented, and, as they are mostly 

 forest birds and poor filers, we may suppose that most of them 

 came to New Zealand in the Eocene Period. But the pigeons, the 

 game-birds, and the Picaria? are each represented by a single 

 species only; and it is, therefore, presumable that they have a 

 later origin than the former. Among the perching birds, the 

 absence of orioles, shrikes, fiower-peckers, swallows, weaver- 

 finches, and others, indicates that they are younger groups than 



