We present population size estimates of mollymawk species at Bollons Island in the Antipodes group based on counts in 1994 and 1995. Totals of 115 pairs of black-browed mollymawks Diomedea m. melanophrys and about 20 pairs of white-capped mollymawks D. cauta steadi were estimated to be nesting. Based on previous counts from Bollons Island and population estimates from other islands in the New Zealand region, we conclude that numbers of D. m. melanophrys have increased in this region, in contrast to D. m. impavida which has decreased. The few data on the population size of D. cauta steadi hint at a population increase in that taxon also.
The densities of Chatham Island pipits (Anthus novaeseelandiae chathamensis) and skylarks (Alauda arvensis) on the south coast of Chatham Island were estimated at 7 individuals km-2 and 10 ind. km-2, respectively. Foraging behaviours used by pipit differed significantly between rough fernland, pasture and beaches. Foraging behaviours also differed significantly between pipits and skylark on pasture, and pipits moved on average 10 times further per minute than skylark. The make-up of pipit foraging behaviour on fields and beaches on Chatham Island also differed significantly from those at Wellington, North Island, during autumn.
The breeding biology of kakerori, or Rarotonga flycatcher (Pomarea dimidiata) was studied during ten years (1987-97) of experimental management aimed at saving this endangered monarch flycatcher from extinction. Kakerori remained territorial all year and were usually monogamous. Most birds kept the same mate from year to year, but pairs that failed to raise any young were more likely to divorce than successful pairs. Despite living in the tropics, kakerori breeding was strictly seasonal, with eggs laid from early October to mid-February, and mostly in late October and early November. Nesting started earlier in years when October was very sunny. Most pairs (74%) laid only one clutch, but some pairs laid up to four replacement clutches when nests failed. Three pairs (1%) successfully raised two broods in a season. Rat (Rattus spp.) predation was the principal cause of nest failure, especially of nests in pua (Fagraea berteriana), the main fruiting tree used by rats during the kakerori breeding season. Annual breeding productivity was initially poor (0.46 fledglings per breeding pair over two years) and the population was declining, but intensive management since 1989 has led to a great increase in productivity (1.07 fledglings per breeding pair over eight years) and the number of kakerori has increased from 29 birds in 1989 to a minimum of 153 birds in 1997. Their IUCN conservation status can therefore be lowered from ‘critically endangered’ to ‘endangered’.
Weka (Gallirallus australis) can be aged accurately up until 50 days old using leg and bill measurements, and then less accurately up to 180 days old using plumage development, wing spur shape and iris colour. Weka less than one year old can be distinguished by their remex tip and wing spur shape. Beyond one year, weka can only be placed into age groups, using wing spur shape.
The rare reversed sexual bill dimorphism of the extinct New Zealand endemic bird species, the huia (Heteralocha acutirostris: Callaeidae) occurs in two Australian riflebird (Ptiloris) and three New Guinea sicklebill (Epimachus [Drepanornis]) birds of paradise (Paradisaeidae). While less extreme than that of the huia, the female bill length proportionate to tarsus length is 7-18% longer than in males. In this proportionate bill length, females are longer-billed than males in most typical (polygynous) birds of paradise. More marked examples of reversed sexual hill dimorphism in the Paradisaeidae occur in species with greater proportions of wood-dwelling arthropods in their diets. Ecological studies of these species might provide insights into the way huia lived and how their bill dimorphism evolved.
We present results of the final stage of the Fiordland crested penguin (tawaki) survey for the area north of Milford Sound. A total of 1,260 nests was counted: 389 south of the Hope River in August 1995, and 871 north of the Hope River between 1992-1994. A further 150 are estimated to occur on the Open Bay Is. The estimated breeding population for tawaki, based primarily on counts of confirmed nests, now stands at 2,260 nests. A realistic estimate of the total number of nests is 2,500-3,000.
The diet of the wrybill (Anarhynchus frontalis) and the banded dotterel (Charadrius bicinctus) was investigated on two New Zealand braided riverbeds using faecal analysis. There was high overlap in terms of taxonomic composition between the two species’ diets, but large variability between individuals. Foods of aquatic and terrestrial (but near-aquatic) origin were consumed; mostly adult beetles (Coleoptera), bugs (Hemiptera) and flies (Diptera). Availability of these prey species relies on a suitable river flow regime.
Large breeding colonies of sooty shearwaters or titi (Puffinus griseus) occur on offshore islands around New Zealand and several smaller colonies occur on headlands and near-shore islands around southern New Zealand; their population trends are unknown. Twelve mainland colonies around Otago had between 11 and 620 burrows in the 1992/93 breeding season. The largest of three near-shore island colonies in Otago had at least 1,050 burrows. Sooty shearwater burrows have been recorded from 39 mainland sites in the South Island, but only 11 (28%) of these have been checked in the last 40 years: many may now be extinct. OSNZ Beach Patrol data suggest that the overall number of sooty shearwaters has changed little over a 26 year period. Methods for monitoring sooty shearwater colonies need to be standardised to evaluate population trends in the future.