Publications Archive

The Chatham Island pigeon or parea (Hemiphaga chathamensis) is an endangered species of pigeon endemic to the Chatham Islands. Effective conservation management of the Chatham Island pigeon required an understanding of its ecology and identification of the causes of decline. We studied the pigeon in their last remaining stronghold; the south-west of Chatham Island, New Zealand, between July 1991 and December 1994. We describe the nesting behav- iour, nesting success, and the dispersal, survival, and recruitment of juveniles. The study was confounded by the lack of information on predator numbers or outcomes of pigeon nests from before the start of predator control activities within and adjacent to our study area. Despite a previously reported decline in pigeon numbers up until the early 1990s, during this study there was a 3-fold population increase, and only a low level of predation by possums and rats. Other than predation, no factor which might previously have limited the pigeon population was identified. We assume that the trapping and poisoning of pest-mammals since 1989, has been sufficient to allow the population of Chatham Island pigeon to recover.

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 Unpublished census results from L. Richdale (1930s-1950s) and S. Sharpe (1950s-1960s) for Otago Peninsula show that there were only 44 nests in 1940, but the number increascd 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 drivcn 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 cnvironment.

We investigated the effect of jetboat wakes on feeding wrybill (Anarhynchusjontalis), banded dotterel (Charadrius bicinctus), black-billed gull (Lams 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.

Bird records from the Snares Islands between Dec 1982 and Oct 2000 are summarised. Population estimates and distributions are given for the 29 breeding species. Bird species recorded breeding on the Snares Is for the first time since 1982 were southern black-browed albatross (Diomedea melanophrys), Chatham Island albatross (D. eremita), mallard (Anas platyrhynchos), southern black-backed gull (Larus dominicanus), fantail (Rhipidura fuliginosa), and starling (Sturnus vulgaris). Fantails are now abundant on the Snares Is. Published work on the breeding chronology and breeding success of 8 intensively studied species is summarised, and new information on breeding ecology is presented for all breeding species. Sighting of 70 non-breeding and vagrant species are summarised; 34 of these were new records from the Snares Is since 1980. The total bird list for the Snares Is is now 99 species, with a further 8 species reported from boats offshore.

The population of white herons (Egretta alba) at Waitangiroto Nature Reserve has been monitored since 1944. The number of breeding adults (estimated from maximum number of nests at the height of the breeding season, and first recorded in 1958) has increased from 26 to c.100, with a concurrent increase in the number of chicks hatched and fledged. Population growth was greatest between 1964-69 and 1980-84. Chick mortality appears to result largely from the effects of westerly and southwesterly storms in October and November, although infanticide, siblicide, and low levels of predation may account for some chickdeaths. The mean number of fledglings nest-I has decreased over time as the number of nests has increased, suggesting a density dependent response. The white herons that “invaded” New Zealand from Australia in 1952 and 1957 did not appear to recruit into the breeding population.