ol. III."] 



1 903 J 



HUTTON, The Cormorants of New Zealand. 



why should the preference for one particular colour, as for 

 crimson in P. onslowi ', go on for generation after generation 

 in one species, while another species had a similar constant 

 predilection for another colour ? Again, why did P. ranfurlyi 

 on Bounty Islands, and P. traversi on Macquarie Island lose 

 their white dorsal patches ? Or why did P. carunculatus, in 

 New Zealand, lose its crest ? Can the loss of a white patch or 

 of a crest, as well as their acquisition, be put down to sexual 

 selection ? 



The loss of the white bars and of the crest is probably due 

 to reversion, and other specific characters may have the same 

 origin. New characters, however, occasionally arose which were 

 not due to reversion. When this took place on continental areas 

 we may, perhaps, attribute their preservation to their usefulness 

 as recognition marks. But this will not help us with those 

 species found only on a single island, or in a single locality far 

 away from other species. Again, the great number of species 

 in New Zealand requires an explanation. The external con- 

 ditions of life for the Cormorants cannot be so great in New 

 Zealand as through America from Canada to Tierra del Fuego, 

 or as in Africa and Asia taken together, and yet there are 

 15 species in New Zealand to 12 in America and 13 in 

 Asia and Africa combined. Consequently we cannot suppose 

 that their specific characters depend directly on external 

 conditions. This is emphasized by the fact that one species 

 — P. carbo — extends continuously from Greenland through 

 Asia Minor and India to Australia and New Zealand. In Aus- 

 tralasia P. carbo never gets so many white feathers on its head 

 as it does in Europe, and is, consequently, sometimes thought 

 to be a distinct variety, in which case the European form must 

 be considered as derived from the Australian one. The real 

 causes of the great number of species in New Zealand are — 

 firstly, it was the meeting place of two migratory streams, one 

 from the Malay Archipelago and New Caledonia, the other 

 from Patagonia ; and secondly, the fact that New Zealand is 

 broken up into a number of islands, lying at considerable distances 

 apart, and which have been isolated for a very long time. 



Turning now to the general characters of the group, we find 

 the generic characters — such as the hooked bill, the rudimentary 

 nostrils, the close, glossy plumage, the short legs and large webbed 

 feet — all eminently adapted to their mode of living. Everyone 

 knows that they obtain their food by catching fish, diving with 

 their wings closed, and using their feet only for propulsion. But 

 on comparing the sub-genera we find characters which we cannot, 

 at present, put down as useful. 



For example, the shape of the bill varies a good deal, being 



