Publications Archive

Abstract Moutohora (Whale Island) holds the largest surveyed breeding colony of grey-faced petrels (Pterodroma macroptera gouldi). For our estimate of the breeding population, we divided the island into 16 sections within which burrow densities were approximately uniform; the surface areas of these sections were found by planimetry. Apparently completed burrows were counted in 1998-2000 within each section by plots of 2 m radius along linear transects, or by 10 X 10 m contiguous plots. The total estimate (± SE) for the island was 109,000 * 10,000 burrows, which equates to about 95,000 pairs breeding annually, given an occupancy rate of about 87%. The population has apparently more than doubled since Norway rats (Rattus norvegicus) and rabbits (Oyctolagus cuniculus) were eradicated in 1985/87.

Hunters of the endemic imperial pigeon (Ducula goliath) or notou in the Foret Plate site, New Caledonia, in Apr 2001 and Mar 2002, allowed us to collect some biological material, measurements and descriptions from 63 pigeons. The sample included 5 immature imperial pigeons, and 58 adults. Several measurements of adult birds differed significantly between the sexes: weight, body length, wing length, tail length, tarsus length, and head length and width being greater in males (n = 28) than females (n = 30). A cross-validated classification using a discriminant function analysis on these variables allowed 74 % of the birds to be correctly classified as male or female. None of We qualitative characters (colour of skin, bill, iris, feet, feathers) was different between the sexes. Sexing birds using a bio-molecular analysis proved to be 100% reliable. The small gonads and the thin wall of the midgut indicated that the notou were not breeding at the time of collection. They had completed, or almost so, their wing moult. Fruits of 22 tree species and the leaves of trees and ferns were identified in material taken from digestive tracts. No internal parasites and few external parasites – of a low pathogenicity – were recorded. These results improve lmowledge of this endemic species and should be useful in this popular game bird’s conservation and management.

Mainland colonies of Australasian gannet (Morus serrator) colonies at Muriwai, northwestem Auckland, New Zealand, were counted between 1999 and 2002. Fences installed in 1981 on the landward side of the colonies were removed at the end of the breeding seasons of 1996 (southern colony) and 1997 (northern colony). Counts 3 years before and after fence removal were compared. After fence removal, the total average number of birds during the peak breeding season (December and January) increased by 65%. The increase resulted largely from an increase in the average number of pairs nesting on the northern colony, and a small increase in the average maximum number of chicks on the northern and southern colonies.

Cook’s petrel (Pterodroma cookii), a New Zealand endemic, now breeds on only three islands at the extremities of its former range. Holocene fossil bones have indicated sites of 11 extinct colonies on North and South Islands, showing that Cook’s petrels preferred hills Gallirallus australis) have endangered these last colonies. Breeding success, most affected by rat predation of eggs and chicks, deteriorated seriously after extermination of feral cats from Hauturu, but improved significantly after eradication of rats from Whenua Hou. Rats are now a major threat on Hauturu. Cook’s petrels should be considered for reintroduction to suitable mainland reserves, to enhance biodiversity and restore nutrient inflows.

The taxonomic status of the endangered orange-fronted parakeet (Cyanoramphus malherbi)) has been the subject of much debate since this endemic New Zealand parakeet was first described in 1857. The debate in the late 1800s and again over the past 30 years has been lively but inconclusive. We provide a summary of this debate and the most recent research into the taxonomic status of this parakeet based on mitochondria1 DNA (mtDNA), assortative pairing, bill morphology, vocalisation, and comparative ecology. Based on all available scientific and historical data, we conclude that the orange-fronted parakeet is a distinct species.

Little is known of the causes of mortality in captive-bred brown teal (Anas chlorotis) released to the wild. To test whether feeding difficulties have contributed to the poor survival of released birds, we developed a method to detect starvation using the wing fat content of brown teal. We extracted the lipids from 4 outer wing components of 17 intact brown teal carcasses. The lipid content of each component reflected the birds’ nutritional condition (based on body mass and size, and visible fat). Lipids were also extracted from the outer wing components of 7 partial brown teal carcasses, 6 of which were from captive-bred released birds whose cause of death could not be determined. All of the released teal were found to have been in very poor nutritional condition immediately before death, implicating starvation as a factor in their deaths. Improving the feeding regime of captive-bred brown teal (pre- and post-release) is likely to increase their survival.

Bellbird breeding activity was monitored on Tiritiri Matangi Is in 1977 and 1978. The density of bellbirds breeding within the study area was 2.13 pairs ha-1. Resighting of banded adult birds in consecutive years was 69% and less than half the pair bonds were maintained into the following season. Breeding extended from Oct to Jan, with a peak in Nov. Most nests were built in tree ferns, and the mean clutch size was 3.6 eggs. Incubation and nestling periods were c. 12 and 14 days, respectively. The female bellbird was significantly more active than the male in care of the nestlings. Measurements of chick head and wing length were correlated with age. Nest success was 44%, and daily survival rate 97%. Predation, desertion, and exposure contributed to nest failure, and re-nesting was common. The mean number of nests female-1 season-1 was 1.3, while mean reproductive success was 2 chicks fledged. Young were independent 2 weeks after fledging, and moulted to adult plumage in their 1st year. The dynamics of the Tiritiri Matangi population, when compared with other populations, suggest that breeding behaviour is a flexible response to environmental factors, and will vary between populations depending on the level of predation, competition and habitat quality.

A quantitative survey of the bird community of Kaitoke wetland, Great Barrier Is., New Zealand between May 1998 and July 2000 using 5-minute counts recorded 33 species, most of which occurred in less than 10% of counts. The commonest species were North Island fernbud (Bowdleria punctata), fantail (Rhipidura fuliginosa), silvereye (Zosterops lateralis), grey warbler (Geygone igata), welcome swallow (Hirundo neoxena) and (collectively) the exotic finches, yellowhammer (Emberiza citrinella), chaffinch (Fringilla coelebs) and goldfinch (Carduelis carduelis). Native wetland species also recorded were spotless crake (Porzana tabuensis), banded rail (Rallus phillipensis), Australasian bittern (Botaurus poiciloptilus), pukeko (Porphyrio melanotus) and Australasian harrier (Circus approximans). Distributional analysis of the commonest species (those occurring in more than 10% of counts) showed most had some association with a particular vegetation type(s), while few showed any change in conspicuousness with season. There was little apparent movement of buds associated with phenology of the main wetland plant species. The sigruficance of Kaitoke wetland in providing habitat for a range of native wetland bud species is recognised. The current threat to this ecosystem from introduced pests and development pressure, and the paucity of data available on native wetland bird species to inform conservation management, is discussed.

The breeding success of northern New Zealand dotterels (Charadrius obscurus aquilonius) on Matakana Island, Bay of Plenty, was determined over 8 seasons (1992/93-1999/2000) in managed and unmanaged areas. Management to enhance breeding success included shifting nests to reduce the risk of flooding during spring tides and storms, and reducing predator populations of brushtail possum (Trichosurus vulpecula), feral house cat (Felis catus), Norway rat (Rattus norvegicus), stoat (Mustela ermines), and southern black-backed gull (Larus dominicanus) at dotterel breeding areas. Measures taken to reduce the incidence of disturbance by people on breeding dotterels included erecting fences around nesting areas, and speaking to members of the public about the plight of the species. The number of breeding pairs on Matakana Island fluctuated between 19 and 31 during the 8 seasons. Overall, 35.1% of 276 nesting attempts resulted in broods hatching. The main causes of nest failure during incubation were flooding by high tides or storms, and predation. The proportion of nests in which 1 or more eggs hatched was fairly stable during the 1993/94 to 1997/98 seasons at 26.1-33.3%, but was 68.0 and 51.3% in the last 2 years. This marked improvement in nesting success was attributed to the increased duration of pest control: starting before dotterel breeding began and continuing until most broods had fledged. Nesting success during incubation in managed habitat (47.5%) was significantly greater than in managed habitat (19.5%). Overall, 52.6% of chicks fledged. The number of chicks fledged per season (5 – 33), and fledglings produced per breeding pair (0.26 – 1.08) increased through the study In conclusion, we make suggestions to further promote the conservation of the northern New Zealand dotterel.