Publications Archive

Morphological comparison of the extinct Huia (Heteralocha acutirostris) with its closest known relatives suggests that the pronounced sexual bill dimorphism of the former evolved through selection on female, rather than male bill form. Because sexual selection acts predominantly on males, it cannot readily explain such dimorphism in a non-polyandrous species. Greater female divergence in foraging-related anatomy in a species in which males are the larger (and therefore presumably socially dominant) sex is, however, consistent with the hypothesis that sexual dimorphism can be an adaptation to reduce intersexual competition for food. Determining which sex changed most is a more rigorous means of establishing the evolutionary significance of sexually dimorphic traits than interpretation of current function.

Measurements of the lengths of fossil bones show that North Island Laughing Owls were appreciably smaller than South Island ones. Humeri and tarsometatarsi from the North Island were on average significantly shorter than those from the South Island. The regressions of humerus length and tarsometatarsus length on latitude were significant, and length and latitude were positively correlated. The North Island samples were too small to establish whether variation was clinal, and in the meantime the continued recognition of North and South Island subspecies seems warranted. KEYWORDS: Laughing Owl, Sceloglaux, fossil bones, geographical variation, subspecies.

Evidence of predation by kiore (Rattus exulans) on Little Shearwater (Puffinus assimilis haurakiensis) eggs was obtained on Lady Alice Island, Hen and Chickens Group, during the 1994 breeding season. A time-lapse video camera filmed a kiore removing a Little Shearwater egg from a nesting chamber. This egg was later recovered, showing signs of damage typical of rat predation. A kiore was also filmed breaking open and eating a punctured hen egg that had been placed in a shearwater burrow. Sixteen (55%) of the 29 nests monitored failed during incubation, and predation by kiore was the probable cause of failure for up to 75% of these nests.

Records of all mollymawk sightings on Bollons Island, Antipodes Islands, are reviewed. Data are provided to confirm the breeding record for Black-browed Mollymawk Diomedea melanophrys melanophrys and add a new breeding record for the NZ White-capped (Shy) Mollymawk Diomedea cauta steadi.

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 census in gardens in Hamilton, 71.8% of the 4428 birds observed belonged to introduced species. A total of 15 species were observed. Bird species richness was positively correlated with native plant biomass and, more strongly, with total plant biomass. More birds were present in gardens with more native plants. Among the most common species, the abundance of the House Sparrow (Passer domesticus) decreased with increasing percentage of native plants, the Silvereye (Zosterops lateralis) increased, while Blackbirds (Turdus merula) and Starlings (Sturnus vulgaris) showed no significant change. This was typical for a other introduced bird species. Most other birds, including the Fantail (Rhipidura fuliginosa) and the Grey Warbler (Gerygone igata), were most abundant in gardens with higher native plant biomass. Notable was the absence of the Tui (Prosthemadera novaeseelandiae) from all censused areas in Hamilton at the time of observation. No significant variation between morning and evening samples was noted.