430 Mr. Tom Iredale on the Surface Breeding 



■way. These starvelings were dwarfed structurally^ and I 

 cannot think that they would ever reach the normal size. 

 It is possible that their systems would be so weakened that 

 they could not survive the first winter's struggle at sea. 

 In other cases it was noted that specimens seemed to have 

 developed strongly and were bigger birds. Indeed, the bills 

 of some of these young giants recalled those of Pterodroma 

 macroptera gouldi (Hutton). 



I was now convinced that it was impossible to indicate 

 any incipient species on the main island, but realising the 

 doubting view of the systematic ornithologist, I resolved to 

 attempt to make assurance doubly sure. 



In the spring, just after the birds had settled, I devoted 

 three days to a tour of the island with the sole object of get- 

 ting reliable data with regard to the variation. Mr. Sidney 

 Oliver accompanied me, and we walked right round the 

 island. The route extended some miles, and every altitude 

 was included, rising from the flat to 1200 feet and falling 

 again to sea-level : then, following the crater rim, it rose to 

 1700 feet, the highest point of the island, and then descended 

 to the commencing place. So that no prejudice should enter 

 into this examination, every bird adjacent to the track was 

 handled, the coloration of the head, breast, belly, and legs 

 written down. It should be noted that the word track as 

 here used does not mean a beaten road, but simply a 

 direction through a virgin bush. Throughout the journey 

 every little variation was carefully noted, but nothing was 

 found whereby forms could be separated. 



On the other hand, the observed variation was found to be 

 so great that we could not definitely match two birds. The 

 darkest birds were almost black above and below, with uni- 

 formly black legs and feet ; the next stage would be dark 

 blackish-grey birds with dark legs and feet : rtLany dark birds 

 would have "^ sandalled" or '^ light legs " (the reason for these 

 italics will be shown later on) : then there would be dark 

 birds, with the belly white or nearly so : these and all the 

 light forms had generally '* light legs," but some light birds 

 were found with U7iif or m dark legs and feet. Birds in which 



