Publications Archive

Winter movements of southern black-backed gulls at Palmer Station, Antarctica, correlate with shifts in pack ice. Numbers of gulls increase when open water appears near shore, exposing foraging sites, and when human wastes are available.

Information on flightlines of starlings (Sturnus vulgaris) to and from roosts is summarised, and a map shows sites and areas served by roosts in the Wellington area. Four offshore islands in the area are used as roosts. In midwinter birds may spend 16 hours nightly in roosts. One roost has remained in use since at least 1913, and others have shifted or been used intermittently. The number of starlings flying to the major roosts in the region has fallen during the 1970s.

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.

The breeding of the South Island robin at Kowhai Bush, Kaikoura, during the 1977-78 and 1978-79 seasons and the mortality from August 1976 to December 1979 are described. Most robins began laying in August and completed breeding in January. Thirty-four percent of their nests were relined “old” ones built in previous seasons by robins or Turdus species. Average time to build a “new” nest was 3.4 days, followed by a prelay period that averaged 4.2 days. Eggs were laid at about 24-hour intervals. Mean clutch size was 2.7 eggs (range 2-4), being smallest in July and largest in October. Incubation averaged 17.7 days, and the females spent 81% of daylight time on the eggs; males did not incubate. In the two seasons, 63% of the eggs hatched and 23% were eaten by predators. Hatching success varied between seasons, months and the four age classes of females. Both parents fed the nestlings, but only the female brooded. Nestlings averaged 20.8 days in the nest, with little or no brooding after day 15. Overall, 42% of the nestlings fledged; most of the rest were eaten by predators. The proportion that fledged decreased as the season progressed because the loss to predators increased. Pairs fledged a mean of 2.1 fledglings in 1977-78 and 2.9 in 1978-79. Juveniles were fed by their parents from 24 to about 50 days, depending on the number of juveniles, how many the female cared for and how soon the next clutch hatched. Mortality was highest in summer for immatures and autumn for adults. Immatures died more in summer, possibly because they were less efficient foragers than adults, but similar proportions of the two age classes died in autumn and winter, perhaps because predation was the main mortality factor.