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In the 1946-47 breeding season the Ornithological Society of New Zealand conducted a census of the gannet (Sula serrator Gray) in New Zealand, the results of which form the subject of this paper. The distribution and annual cycle of the gannet are outlined, field work and methods of estimating the gannet population are described, and historical records summarized. In the main part of the paper, 32 gannet stations are catalogued and described, and their status and population assessed with the help of aerial photographs to supplement observations on the ground. The gannet population is assessed as 21,033 pairs, but may be as low as 18,000 or as high as 24,000, the large margin of error being due to inter- and intra-seasonal variables which cannot be determined at present. Although gannet colonies are distributed from the north to the south of the main islands of New Zealand (34˚ to 47˚ S lat.), 99.7 per cent. of the population breed north of 40˚ S. in sub-tropical waters. Scant historical data suggest that the population has increased during the past century. Finally, suggestions are made for future work on the gannet in New Zealand.

The period covered by the laying of the eggs was not observed in any of these three nestings. It is obvious that such a record will be very difficult to obtain. Incubation Periods. – No. 1 nest, either 29 or 30 days. No. 2 nest, 28 and 29 days, or more. The bird was already incubating when found by Mr. Stidolph, so the period could easily have been longer. No. 3 nest, no record; nest found after incubation had well begun. Hatching to Flying Periods. – No. 1 nest, something under 49 days; not a complete record; date of first flying was missed. No. 2 nest, one chick flying weakly at 50 days; one scarcely flying at all at 50 days. No. 3 nest, one chick last seen at 46 days; no sign of flying; it did not even extend its wings when running at its utmost so should have taken well over 50 days to fly had it lived. The early nesting record of 1949, two eggs on September 11, has apparently been improved upon by one day, i.e., two eggs on September 10, 1950. It appears that this early nesting is not general. Buller, quoting Potts, states that eggs and young have been seen in October and November. Guthrie-Smith (“Mutton Birds and Other Birds,” pp. 102-104) states that they arrive on the breeding grounds on Stewart Island about the middle of October. However, some must arrive earlier, since he found a tiny chick on November 7. From the evidence obtained at Clevedon it would seem that the first egg of the clutch would have been laid about October 3 and the birds would have been present for some time before that date. Falla, 1940, mentions territorial attachment from September 1st onward. The dates given by these writers probably indicate the normal commencement of the breeding season.