28 Bell, Breeding Habits of White Tern. [.sf^'juiy 



of young wood or l)ark, so that the whole looks not unlike a 

 miniature volcanic crater or a small, funnel-shaped pit, with 

 usually, though not always, a slightly raised rim. Somewhat 

 similar places may be formed by dead branches dropping off, 

 leaving a sort of socket. Such places are very common on 

 pohutukawa trees, are no doubt formed in various ways, and are 

 the chosen laying-places of about four-fifths of the White Terns. 

 I have sometimes watched the birds at work on these places. 

 They stand on the edge of the selected place (or pit, as I shall 

 call it) and work round sideways, advancing the right foot first 

 and scratching at the edge of the pit with the left. When they 

 have worked round five or six times they stop, take a step or two 

 backwards, and carefully examine what they have done, picking 

 up with their bills any bits of loose bark they may have scratched 

 off and casting them away. This operation is repeated until all 

 the loose bark is cleared from the proposed laying-place. Occasion- 

 ally both birds work at the pit together, each with its head over 

 the other's left shoulder ; but this is rarely done, as the pit is usually 

 too small for two birds to work at together. It was noticed that 

 whenever an egg was found the bark or wood about it was always 

 most carefully cleaned. 



Whenever the White Terns lay on a pit it is either a very large 

 or a very small one. This is a rule to which there is practically 

 no exception. The larger pits are never less than 8 or lo inches 

 in length (often they are much more), and any width from i to 

 6 or 8 inches. They generally have very little rim. They are 

 usually sloping, and sometimes very steep. A fair number of birds 

 lay in such places, but whenever they do the egg is always placed 

 at some point where no rain water can collect about it. The 

 small hollows are, however, much the more favoured laying- 

 places, perhaps because they are more numerous ; but, in any 

 case, two-thirds of the birds use them. These pits are from 

 about half to one inch across, and usually circular, so that 

 when the egg is in position it is usually supported all round, 

 and stands well above the surrounding wood or bark. I do not 

 remember having seen an egg with more than about a third 

 of its bulk below the level of the ring of bark, and generally 

 it is placed much higher. In some cases the pit on which the 

 egg is laid is so small that I have actually seen the egg totter when 

 the bird retired at my approach. The only reasons for the egg 

 being placed so high that I can at all understand is, firstly, to 

 prevent any rain water which may collect in the pit in heavy 

 weather from coming in contact with the egg ; and, secondly, to 

 allow the parent bird while incubating to almost — or, I believe, 

 in most cases entirely — envelop the egg with its very long breast- 

 feathers. I believe that the eggs are, in most cases, completely 

 enveloped by the feathers of the birds while incubating, for, when 

 sitting birds are approached very closely — and sometimes one 

 can get within arm's length — they always leave their eggs. Their 

 mode of doing so is suggestive, for they first begin to rise on their 



