Publications Archive

The measurements of male and female brown creepers (Finschia novaeseelandiae) were compared to determine whether they are sexually dimorphic and, if so, which characters can be used to distinguish the sexes. In all the measured characters males were significantly larger than females. Possible selective advantages of the brown creeper’s sexual dimorphism are discussed. Wing length was found to be the most reliable discriminator of sex.

The red-footed booby (Sula sula) colony on Mabualau Island, Fiji, was visited from 1980 to 1982. Eggs were recorded throughout the year, and young were found in seven of the nine months of the year considered. The two peaks of nesting recorded were about 7-8 months apart. Only unsuccessful birds were likely to nest twice in the same year. Fledging success was low in both 1980 (55%) and 1981 (24%). Climatic factors rather than food supply or predators caused most mortality. The diet comprised flying fish and squid. Growth was similar to that on Aldabra Atoll, but fledging weight was higher. The timing of the breeding seasons is discussed.

The breeding of the Chatham Island warbler (Gerygone albofrontata) was studied over five seasons on three islands in the Chatham Island Group. The breeding season is short, and only one brood is raised per year. On predator-free ‘petrel islands’, nests were low to the ground in dense vegetation, whereas on Chatham Island nests were high and in the open. Mean clutch size was 3.1 eggs (n=79). Incubation and nestling periods were both about 20 days. Density of breeding birds was highest in regenerating forest clumps on predator-free islands, with about 10 pairs per hectare. Comparisons are made with the breeding biology of the grey warbler (G. igata) of the New Zealand mainland and with other Gerygone species. Brood parasitism by the shining cuckoo (Chrysococcyx lucidus) and how vulnerable the Chatham Island warbler is to extinction are discussed.

Grey warblers (Gerygone igata) at Kowhai Bush, Kaikoura, apparently moulted once annually – between January and March. They nested in 19 kinds of trees and shrubs – mostly small-leaved species, especially kanuka, the dominant plant in the study area. Behaviour associated with selection of the nest site is described. A list of materials used in building is given. On average, nests were 14 cm long and just over 7 cm wide. Nearly half the nests hung freely from their upper attachment; others also had attachments laterally and below. The entrances of nests were non-randomly orientated in 1976 but not so as to face away from prevailing winds. Copulation is described. Three eggs in September were laid close to sunrise. Late eggs were wider on average than early ones but no different in length. The constant that related fresh weight of eggs, length, and the square of width was 0.598. Eggs lost about a quarter of their weight during incubation. Grey warblers hatched with natal down distributed in eight main and two minor patches. The physical and behavioural development of nestlings is described. A sample of 19 nestlings had been fed invertebrates of six orders. Caterpillars occurred in 90% of stomachs and made up 42% of ingested items. Spiders were next most important of total items. Nestlings were parasitised by the blood-sucking mite Ornithonyssus bursa. Fledglings had distinctive dark brown irides and yellowish facial plumage until February-March, when they moulted to adult form. Males played the greater role in caring for early fledglings while the female built the late nest. Young males seemed rarely to be successful in holding territory the summer after that in which they were reared. Brood parasitism by shining cuckoos was the main cause of failure of late eggs (though a relatively minor factor overall); mammalian predation was the greatest single cause of nestling mortality.