Publications Archive

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.

Since the first burrows of Chatham Island Taiko Pterodroma magentae were found in 1987/88, trapping around the burrows has killed 204 feral cats Felis cattus, 3053 Possums Trichosurus vulpecula, 1572 Weka Gallirallus australis and 589 rats Rattus spp. in 109,892 trap-nights to March 1993. No Taiko are known to have been killed by predators. Productivity was static at one fledgling per year until 1992/93, when two fledglings were reared. Unobtrusive studies of breeding biology indicated that mating occurred about 1 October, laying about 26 November, hatching about 20 January and fledglings departed about 4 May. The pre-laying exodus of females lasted up to 50 + days and chick-rearing took about 105 days.

The Incredible KiwiKiwis. A Monograph of the family ApterygidaeKiwi – A Secret LifeHandbook of Australian, New Zealand & Antarctic Birds. Vol I, Ratites to Ducks

Forest of several types covered 45.14% of South East Island, Chatham Islands (218 ha). All petrel burrows in 200 10 m2-quadrats in modified and unmodified forest were counted during breeding seasons in 1989 and 1990. From the total of 2675 burrows (1.338 burrows m-2 of forest), we estimated a breeding seabird population of more than 1.3 million pairs. The main species were White-faced Storm Petrels (Pelagodroma marina) (840,000 pairs), Broad- billed Prions (Pachyptila vittata) (330,000 pairs), and Southern Diving Petrels (Pelecanoides urinatrix) (127,000 pairs). Smaller numbers of Sooty Shearwaters (Puffinus griseus), Grey-backed Storm Petrels (Oceanites nereis) and Chatham Petrels (Pterodroma axillaris) also bred in the forests. Comparisons are made with population estimates for other New Zealand islands, parts of the Galapagos Islands, Baccalieu Island (Newfoundland), and the Juan Fernandez group. Conservation issues for South East Island are discussed.