Publications Archive

North Island kokako (Callaeas cinerea wilsoni) appear sexually monomorphic. Females are, on average, slightly smaller than males in most body measurements. Mean tarsus length was significantly smaller among females at all sites and can be used to predict sex of unknown birds with up to 86% accuracy. A simple discriminant function, using tarsus and wing chord measurements, was derived which increased sex resolution to over 90% at some sites. This is sufficient accuracy to provide a useful field technique for kokako research and conservation management. Best discriminant functions for different sites are presented and their geographical limitations are discussed.

The yellow-eyed penguin (Megadyptes antipodes) on the South Island of New Zealand was believed to have suffered a population decline that continued into the 1980s. Unpublished census results from L. Richdale (1930s-1950s) and S. Sharpe (1950s-1960s) for Otago Peninsula show that there were only 44 nests in 1940, but the number increased in the 1940s-1960s. Numbers peaked at 276 nests in the mid-1980s. Subsequent decreases and a crash to 79 nests in 1990 led to concerns for the viability of the population, but years of good survival and breeding allowed a recovery. The fluctuations were probably driven by interplays of human impacts and environmental variation. Reservation of breeding areas, revegetation, and predator control have reduced the deleterious human impacts and given the species a chance to increase numbers and withstand adverse fluctuations in the environment.

We investigated the effect of jetboat wakes on feeding wrybill (Anarhynchus frontalis), banded dotterel (Charadrius bicinctus), black-billed gull (Larus bulleri), and black-fronted tern (Sterna albostriata) on the Dart River, Otago. We found that all species feed in areas likely to be affected by jetboat wake. On average, banded dotterel (n=8) were 43.2 mm above the water level and 4.37 m from the waters edge, wrybill (n= 16) were 49 mm above the water level and 0.8 m from the water’s edge. Jetboat wake (n=7) extended 91.3 mm above the waters edge and on average 1 m from the edge of the river channel. The implications of the wash and the extent of the likely effect are discussed.

An annotated checklist of the bird species of Niue Island in the southwest Pacific is provided from published and unpublished sources, and from observations during April-May, September, and December 1994. Results for common species were derived from five-minute counts, numbers seen per kilometre while travelling by motorcycle along roads, and single species surveys. The number of species on Niue is 31 (6 seabirds, 10 shorebirds, and 15 land birds). The common noddy (Anous stolidus) was confirmed as nesting on the island. Recommendations are made for the future management of the hunted Pacific pigeon (Ducula pacifica) and the scarce blue-crowned lory (Vini australis).

We studied North Island robins over 7 breeding seasons following their reintroduction to Tiritiri Matangi Island. All robins bred in their first year if a mate was available. They usually retained pair bonds for life but some females switched mates within or between breeding seasons. There were 2 instances of sequential polyandry, where a female laid a clutch with a new male while her previous mate was rearing her fledglings. The 1st clutches were usually laid in early September and the last clutches in late December or early January. Mean clutch size was 2.3 eggs, and clutches were largest in the middle of the breeding season. Females reared a maximum of 3 broods per year, and a maximum of six fledglings. Females that survived the breeding season fledged an average of 2.48 young, and 51% of clutches found before hatching fledged at least one young. Juveniles were fed for 4- 7 weeks after fledging, and stayed in the natal territory for 7-10 weeks. Dispersing juveniles were often chased when entering other territories, but there were 4 instances of juveniles being fed by unrelated lone males. The juvenile survival rate declined as the population grew. Permanent territories were restricted to patches with a canopy of at least 6 m, totalling about 13.4 ha, and the breeding population levelled off at 65 in the 5th year. The decline in juvenile survival was similar for males and females, suggesting that both sexes needed to compete for territories even though there were always males without mates because of an initial bias in sex ratio. Males had delayed plumage maturation whereby they appeared similar to females or juveniles until after their first breeding season. We suggest this could be advantageous for territory acquisition because male territory holders cannot be preferentially aggressive toward juvenile males.

This paper describes the activity of garden, bush and riverine birds in the western Hutt hills, 1981-92. The area is 15 km north of Wellington, 7 km north of the Hutt River estuary, and 15 km south of Pauatahanui Inlet, Porirua Harbour, on the southwest coast of the North Island. Observation is based on 35 years’ residence and >12 500 10-min counts conducted between 1981 and 1992. Species first seen each day are distinguished from those first heard. Whenever possible the birds’ food was recorded. The western hills have fewer native passerines than similar habitat on the eastern hills. Several species increased or decreased during the study. Some apparent decline was attributed to the author’s hearing loss. Wind reduced bird detection. Nectar of New Zealand flax (Phormium spp.) was eaten by silvereyes (Zosterops lateralis), tui (Prosthemadera novaeseelandiae) and starlings (Sturnus vulgaris) at different times. In the study area there were about 0.9 cats (Felis catus) per household, a potential predator on birds.