Publications Archive

Previous observations on Pycroft’s petrel (Pterodroma pycrofti) are summarized and distribution of the species is discussed. There are no records north of New Zealand, nor any to the south of the breeding-grounds. The nesting habitat is described, especially with reference to the apparent preference of Pycroft’s petrel for pohutukawa (Metrosideros excelsa) forest. Eggs are laid during the last week of November and the first week of December, with a peak on 26 November. Incubation is commenced by the male. Repeated desertion is discussed, with shortage of food reserves as a possible cause. Incubating birds lose 3–4 gm. per day. The mean weight for the species is 159 gm. On the breeding grounds eighty-one per cent of the population are unemployed birds. The proportion of unemployed birds in other petrel populations is discussed. The activity of breeding birds is compared to that of unemployed birds. Unemployed birds are responsible for calls heard over the colony in the air, most breeding birds arriving inconspicuously. The unemployed population may exert a social stimulus on the breeding birds. In the Appendix, individual burrows are described. Frequent reference has been made to the literature on petrel behaviour and ecology, and work on some important aspects is reviewed.

On six surveys of Swain’s Island in 1966 and 1967, field workers of the Smithsonian Institution’s Pacific Ocean Biological Survey Program recorded 16 species of birds: 9 central Pacific seabirds, 5 Arctic shorebird migrants, and 2 migrants from the southwest Pacific. Three species of seabirds (brown noddy, black noddy, and white tern) breed on the island and a fourth (white-tailed tropicbird) probably does so. The other species of seabirds recorded from the island (sooty tern, black-naped tern, frigatebird sp., red-tailed tropicbird, and red-footed booby) probably occur on the island only as visitants. Three of the shorebirds (golden plover, ruddy turnstone, and wandering tattler) are common and regular migrants to the island; the other two species (bristle-thighed curlew, sanderling) occur much less frequently and in much smaller numbers. One of the two migrants from the southwest Pacific, the reef heron, is apparently of irregular or uncommon occurrence while the other, the New Zealand cuckoo, is present in small to moderate numbers throughout much of the year.

The following is intended only as a relatively brief narrative of the Ornithological Society of New Zealand’s 25th Anniversary Expedition to the Kermadec group. A general account of the bird life and other more specific papers resulting from ornithological studies undertaken by the expedition will appear in “Notornis” at a later date.

A study of the stomach contents of 124 harriers showed their food to be predominantly birds, mammals and insects, occasionalIy frogs and fish. Birds taken were mainly house sparrows, blackbirds, song thrushes and skylarks. Mammals, often eaten as carrion, were rabbits, hares, Australian opossums, and hedgehogs. Insects frequently present were crickets, grasshoppers and locusts (Orthoptera) and cicadas (Hemiptera). Macerated plant material, found in many specimens, came from the gut of prey. Fresh plant fragments appeared to have been taken accidentally. The proportions of each kind of food varied seasonally but all the main categories were represented in stomachs throughout the year. More than half the specimens contained only one food, the rest a mixture of two or more.