Publications Archive

The breeding biology of the paradise shelduck (Tadorna variegata) was studied on hill-country farmland west of Tokomaru Bay, New Zealand, during 1973–1976. Throughout the breeding season the shelduck population comprised territorial pairs, which occupied areas of pasture surrounding stock ponds or other water bodies, and flocks, which were mostly of juveniles and which remained at specific sites on river terraces or hillsides. Breeding was attempted only by the territorial pairs. Prospecting for nest sites started in late June and 62% of 47 nests found were in hollow logs on the ground. Laying began in August and the mean size of 36 clutches was 9.4. Of 282 eggs, 5% were infertile and 87% of the fertile eggs hatched. Only 20% of the pairs which lost their clutches re-nested. Ducklings were reared on stock ponds, in streams or rivers, and in swampy soaks on hillsides. About 60% of the ducklings reaching the rearing areas survived the 8-week fledging period. The main causes of duckling mortality were bad weather and predation by feral cats. During their first week, ducklings fed mostly on aquatic insects, and thereafter on plant material. Of 67 ducklings which fledged, 54.7% were males, and, after fledging, males dispersed more widely than females.

Letter to the Editor, 13 June 1979

The history of ornithological activity in the Hunua Ranges, south-east of Auckland, is outlined. An account is given of both native and introduced birds from 1888 to 1978.

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.