Publications Archive

Between 1960 and May 1993, 62 species of seabirds were recorded at Chatham Islands, including 43 procellariiforms, 5 penguins, 5 pelecaniforms, and 9 Lari. Apart from the 24 breeding species, there were 14 regular visitors, 13 stragglers, 2 rarely seen on migration, and 9 found only beach-cast or as other remains. There is considerable endemism: 8 species or subspecies are confined, or largely confined, to breeding at the Chathams.

In late July and early August, 1993, the survey of Fiordland Crested Penguins on Codfish I. initiated by Department of Conservation personnel in 1992, was completed. From 11-19 August we surveyed the coasts of southern Stewart and the Titi Is, and from 21-23 August we surveyed Solander I. A total of 115 Fiordland Crested Penguin nests and 300 birds were counted: 5 birds on or near Codfish I., 32 birds around southern Stewart I., and 115 nests and 263 birds on Solander I. Solander I. has been added to the small number of locations where more than 100 penguin nests are found annually. The survey has now covered all of the range of the Fiordland Crested Penguin except for the mainland north of Milford Sound; our estimate of nests in the surveyed area is about 1000 annually.

Morphometric data are presented for the northern and southern populations of the NZ Dotterel. There are significant differences between the two populations in all measurements of birds and eggs. The differences in midtoe and adult weight are pronounced: the former yields a Coefficient of Difference above the conventional level of subspecific difference. Plumage differs between birds of the two populations. Ecologically and behaviourally the two populations differ distinctly; southern birds breed inland and northern birds on the coast, the timing of flock break-up and movement to breeding sites is different and the ranges of the two groups are discrete. Based on these differences, the two populations are accorded subspecific status, and a new subspecies is described.

South East Island (Rangatira) is the most important reserve for oceanic and terrestrial bird life in the Chatham Islands, and one of the largest islands free of mammalian predators in the New Zealand region. The avifauna consists of 66 species: there are confirmed records of breeding or attempted breeding for 33 of these. The rest are either vagrants or forage in adjacent waters. Two species, Shore Plover Thinornis novaeseelandiae and Chatham Petrel Pterodroma axillaris breed only on this island. A further six species are endemic to the Chathams, but are rare elsewhere in the group; five of them are abundant. Historical and contemporary records are covered. During the past 150 years, the vegetation of the island has been altered substantially, by fire and grazing. The changes have influenced the fauna greatly, and its original composition and character are unclear.

The southern third (1300 ha) of the Waipapa Ecological Area, Pureora Forest Park, was surveyed for North Island Kokako (Callaeas cinerea wilsoni) during the summer of 1990/91. Thirty four territories were located (0.03 territories ha-1). At least 17 of these territories contained a pair, four (23%) of which fledged a total of seven juveniles. A conservative estimate of density was 0.04 Kokako ha-1 over the whole study area. These results suggest that there has been a large (up to 60%) decline in Kokako density in the Waipapa Ecological Area since the previous survey in 1980-81.

We investigated foraging niche overlap in two allopatric and two sympatric island populations of Petroica species. We predicted that sympatric populations (Black Robins, Chatham Island Tits) would have narrower foraging niches than the allopatric populations (South Island Robins, Snares Tits), and that the foraging patterns of the allopatric populations would tend to be intermediate between the sympatric populations. These predictions were not supported. Rather, the two robins and two tits foraged in ways very similar to each other, and in ways suggesting that “robin” and “tit” foraging styles are a conservative feature in the evolution of this group.

A survey of Blue Penguins (Eudyptula minor) in 1991-92 along the coast of Otago in the South Island found at least 2073 breeding pairs between the Waitaki River and Nugget Point. The total population in this area, including immature birds, is estimated at about 9300 birds. These birds use 20 breeding sites along the coast, but most (97%) are concentrated in four areas – Taieri Island, Green Island, Otago Peninsula and Oamaru. Birds no longer breed at seven sites, have decreased on Green Island and at one site on Otago Peninsula, remained largely unchanged at Nugget Point and have recently increased at Pilot’s Beach near Taiaroa Head, and possibly at Oamaru. Dogs killed at least 34% of birds breeding in one part of Oamaru. Most nests were in depressions completely covered by vegetation (39.6%) or in burrows dug into soil (36.9%) but the proportions of burrow types differed between sites. Introduced mammalian predators had little or no access to most sites; where predator access was unrestricted, some predator control was usually in place.

In March 1992, we counted Southern Buller’s Mollymawks Diomedea b. bulleri breeding on the Snares Islands. A total of 7683 occupied nests was counted and a further 777 estimated, giving a total of 8460 breeding pairs. The number of occupied nests counted in 1992 is 78% higher than the number counted in 1969. Although more breeding pairs were present in 1992 than in 1969, with only two counts 23 years apart, it is not possible to determine the current population trend in relation to fisheries activities.

The Chatham Island Taiko Pterodroma magentae (Aves: Procellariidae) was rediscovered on 1 January 1978 in its traditional breeding grounds in the Tuku Gully in the south west of main Chatham Island. The history of efforts to rediscover Pterodroma magentae (known as the Magenta Petrel) and to identify the mysterious Chatham Island Taiko are described. The identity of the Chatham Island Taiko and the Magenta Petrel is confirmed. Aspects of behaviour, habitat, morphology, and ecology of the species are reviewed. To date, 42 Taiko have been banded; 12 recaptures suggest a population of over 100 birds. Night observations of flying birds and times of burrow use indicate that the breeding season extends from mid-September to mid- May. Efforts to discover the breeding grounds before the assistance of radio telemetry are summarised.

The total population of New Zealand King Shag (Leucocarbo carunculatus) was counted for the first time during the 1992 breeding season. At 524 birds, numbers were almost twice as high as estimated previously. The daily rhythm, foraging range and feeding location of King Shags from the Duffers Reef colony in the Marlborough Sounds were studied in 1991 and 1992. The mean (( s.d.) foraging range was 8.2 ( 4.1 km (maximum 24 km) from the colony. Most (74%) fed in 31% of the study area, 20-40 metres below the surface on a mainly flat bottom, within the confines of the outer Marlborough Sounds. During the six months courtship/breeding period, daily rhythm of the colony was different from the rest of morning and afternoon. It is assumed that females left to feed in the morning and males in the afternoon to feed and collect nesting material. No double peak was seen during the non breeding period.

The endemic New Zealand Shore Plover (Thinornis novaeseelandiae) is confined to a small population on Rangatira (South East Island) in the Chatham Islands. There are about 43 breeding pairs and 130 adults. The population is sedentary. Shore Plover form monogamous breeding pairs in separate defended territories. Clutch size, parental behaviour, courtship, and defence displays are similar to those of other plovers. Shore Plover have several unusual breeding characteristics which may be responses to the relatively constant environment and limited area of habitat on Rangatira, low prey abundance, differences in habitat quality, no mammalian predators, and the presence of certain avian predators. Shore Plover are unique among plovers in nesting under cover, which protects their nests from avian predators and temperature extremes, but which would make nests very vulnerable to predation by mammals. Environmental conditions on Rangatira may also be a reason for the high hatching rate, low chick survival, and differing breeding success within the population.