Publications Archive

Pellet casting was studied in a population of South Island robins (Petroica australis australis) at Kowhai Bush, Kaikoura from April 1977 to July 1978. Pellet regurgitation is described. Casting has a diurnal rhythm. Monthly regurgitation rates reflected the diet of the robins, with the highest rates occurring in the summer months when the main food is berries and invertebrates with their indigestible seeds and exoskeletons. It was calculated that, during February 1978, the month of highest mean egestion rate, a Robin would egest six pellets per day. The effect of age and sex on the frequency of castings is discussed.

Dr Pat Vickers Rich. Bulletin 184. Bureau of Natural Resources, Geology and Geophysics. Canberra 1979.

The feeding ecology of the wrybill (Anarhynchus frontalis) was compared between two sites – a flood-prone riverbed and a stable riverbed. Larvae of aquatic insects, particularly mayfly (Deleatidium spp.), were the main prey of wrybills, which captured them by a variety of methods. The sideways-bent bill was useful in capturing insects from the under-surface of stones where they would normally have been inaccessible to birds with shorter, straight, or even up-curved bills. The evolutionary significance of the bent bill is discussed with reference to climatic trends during and since the Pleistocene period. During floods, aquatic prey was relatively unavailable to wrybills, causing them to switch to riparian foraging.

Stationary and walking counting methods to obtain numbers of bird species in survey work were compared under Tasmanian forest conditions. For short observation times, the stationary method was clearly inferior to walking at a brisk pace through the survey area. In unsheltered areas, windy conditions significantly reduced the number of species recorded compared with calm conditions in either fine or rainy weather. When time is short, a basic 10-minute walking unit will yield a reasonable percentage of the number of species present.

Recent observations and counts of chicks suggest that predation by rats and cats may be destroying the sooty tern (Sterna fuscata) colony at Denham Bay, Raoul Island. Aspects of this predation and of a comparable situation on Ascension Island are discussed. More management-oriented research is needed on the sooty tern at Raoul Island, and an annual assessment of breeding success and population trends is proposed.

The breeding and habits of the Antarctic tern (Sterna vittata) were studied during a summer at the Snares Islands. Daily records were kept of ten nests situated on cliff ledges and rocks. Egg-laying occurred during two periods; late October/early November and late November. The usual clutch was one egg, but some two-egg clutches were laid. Re-laying probably occurred on one occasion when the first clutch was lost. Both parents incubated, and the incubation period averaged 24 days. The chicks were guarded for two to three days after hatching and were fed by both parents. Chicks fledged between 27 and 32 days after hatching. Adverse weather severely restricted chick growth during the early stages of development and was a major factor in chick mortality.

Factors causing predation of the clam paphies (Mesodesma ventricosa), the well-known ” toheroa,” by black-backed gulls are described. Counts of black-backed gulls made at approximately monthly intervals along a 23 kilometre stretch of beach between January 1970 and January 1971 and in December 1972, together with further observations between 1968 and 1975 show that black-backed gulls are important predators of toheroa.