Publications Archive

When interpreting counts of forest birds it is seldom possible to distinguish the effects of changing density from those of changing conspicuousness; these often arise from the birds’ singing and calling. To investigate this, birds first seen were recorded separately from those first heard when counting birds in forest of the Orongorongo Valley, Wellington, New Zealand. Apparent changes in the frequency of Paradise Duck (Tadorna variegata) in the river valley, and of the Song Thrush (Turdus philomelos), Whitehead (Mohoua albicilla), Grey Warbler (Gerygone igata) and Chaffinch (Fringilla coelebs) in the forest coincided with changes in the frequency of their singing or calling; they were considered suspect. Changes in the frequency of the Black-backed Gull (Larus dominicanus) on the riverbed, and of N.Z. Pigeon (Hemiphaga novaeseelandiae), Blackbird (Turdus merula), Fantail (Rhipidura fuliginosa), Silvereye (Zosterops lateralis), Bellbird (Anthornis melanura), Tui (Prosthemadera novaeseelandiae), and Australian Magpie (Gymnorhina tibicen) did not show a similar correlation. Special study of the ways in which birds either advertise or conceal themselves is needed. Correction factors may never compensate completely for the effects of the birds’ varying conspicuousness.

Captive Weka (Gallirallus australis) were offered two species of native frogs (Leiopelma hochstetteri and L. archeyi) as prey. The anti-predator behaviour and/or gland secretions of the frogs were sufficient to avoid damage and allow them to escape. The leaf litter habitats where frogs occur in the Coromandel Ranges are least likely to be favoured by Weka. Objects under which frogs were found were heavier than those generally moved by Weka while foraging. Weka seem to constitute less of a risk to frogs than earlier believed.

We studied Cape Pigeons Daption capense at The Snares, one of its northern most breeding sites, from pre-laying to fledging during 1985/86 and 1986/87, and compared our data with those from other localities. At The Snares, mean laying dates were 10 November 1985 and 8 November 1986, mean hatching date was 25 December 1985, mean fledging date was 14 February 1986, breeding success was 58.7% in 1985/86 and 50.0% in 1986/87, and adult male annual survival was 94%. Laying mainly begins later at higher latitude breeding sites and there are differences in pre-laying colony attendance between some populations. Incubation and nestling periods are similar throughout the species’ range suggesting an inherent rather than environmentally-induced explanation for the relatively short nesting season of fulmars compared to other petrels.

During a visit to North Brother Island in Cook Strait from 11 October to 6 November 1990, we estimated by quadrat sampling that the 4 ha island supported 1000 pairs of Fairy Prions, 600 pairs of Common Diving Petrels, and 225 adult tuatara. Most Diving Petrels nested below Coprosma scrub, and a few eggs were laid on the surface under dense shrubs. Many prion burrows were in more open vegetation. Burrows of both species were simple and were not shared with tuatara. Some evidence of tuatara preying on unattended eggs was found, but there was no evidence that the endemic Sphenodon guntheri, which is smaller than S. punctatus, fed on adults of either species. Many Diving Petrels, prions, Fluttering Shearwaters and Red-billed Gulls fed in tide rips close to the island. The position of each species in feeding assemblages was related to their dive depths. Diving Petrels in areas of strong currents submerged for only a few seconds at a time, but in areas of calm water dive durations averaged 29 seconds.

Pipit (Anthus novaeseelandiae) numbers on nine count routes in the Wellington region ranged from 0.16 to 6.22 per km on average. Estimated densities in regions with some favourable habitat varied between 1.0 and 2.5 per square kilometre. Highest numbers were in the hills south and west of Karori, and on the southern and western beaches between Owhiro Bay and Titahi Bay. Densities were lower over the rest of the region due to intensive farming, unfavourable plant succession pathways to bush, and urban development.

On Ewing Island, Auckland Islands, during the austral summer of 1991-92, Auckland Island Teal Anas aucklandica aucklandica were dispersed principally as pairs occupying and vigorously defending small all-purpose territories. Most territories were around the margins of the island, either within a narrow fringe of grassland, or at the very edge of Olearia lyallii forest with access to boulder beaches or low wave platforms. Few territorial pairs lived entirely within the forest. A small number of juveniles and unpaired adults assembled as a flock at one protected coastal location where food was super-abundant, but other unpaired birds appeared to live furtively around the margins of occupied territories. Some non-territorial pairs persistently tried to occupy sections of shoreline in the face of defence by territorial pairs. Only territorial pairs were observed breeding. Females sited their nests on the ground well hidden from view above and laid eggs each of which weighed, on average, 14.8% of body mass. Mean clutch size in 45 nests was 3.4 eggs and hatching success of 86 eggs was 93%. Ducklings were first seen on 11 December and most broods had been reduced to a singleton within eight days of hatching. The probability of a duckling surviving from hatching to 30 days was 0.272. The estimated mean size of extant broods at fledging was 1.6. By estimation, only 14% of ducklings may survive to fledging, and up to two-thirds of all breeding pairs may fail to raise any young. Re-laying by unsuccessful pairs may extend the breeding season into April. Males contributed fully to care of the brood but were not always seen in close attendance. By comparison with other related Australasian teals, Auckland Island Teal have a more terrestrial lifestyle and show more enduring territoriality.