A New Nesting-site of Cook's Petrel Pterodroma cooki
[Read before the Dunedin Science Congress, May, 1935; received by the Editor, May 1, 1936; issued separately, December, 1936.]
Pt. cooki, which, so far as is at present known, nests only in New Zealand waters, had until the end of last year been recorded as breeding on Little Barrier and the Hen and Chickens to the north of Auckland. Two years ago R. A. Falla discovered that Pt. pycrofti nested on the Hen, and as during a five weeks' stay there at the end of 1933 I found no Pt. cooki, but only Pt. pycrofti, breeding on the Hen and Chickens, I think that probably the only extensive nesting place of Pt. cooki in the north is on Little Barrier Island. It was therefore of considerable interest to me to find it at the end of last year nesting in great numbers on Codfish Island, off the north-west of Stewart Island. Mr Falla, who had been through Foveaux Strait in October, wrote me that he had seen about a dozen petrels that looked like Pt. cooki off Puysegur Point. On December 18th I found a Cook's petrel sitting on an egg laid not more than three or four days previously. We subsequently dug out a number of burrows, and the state of the eggs indicated that laying had commenced here about December 12th, which is some weeks later than is the case on Little Barrier. The birds were plentiful on Codfish Island, their burrows being everywhere from 15 feet above sea level up to the tops of the bush. The entrance to the burrow was almost always in rather steep ground, usually among the roots of trees, and many of the burrows were of great length. The shortest we found was about 4 feet, while the longest we dug out was 12 feet; but many that we gave up because they were too deep may have been longer. The average length was probably about 7 feet.
It is strange that Cook's petrel should have but two nesting-places in the New Zealand region, one at the north and one at the south, separated by nearly a thousand miles by sea. This petrel is very numerous on Little Barrier, I am told, and on Codfish Island a rough estimate indicated that there were over twenty thousand burrows.