The establishment since 1984 of small of takahe (Porphyrio mantelli) on four predator-free islands has been an important component of the conservation strategy for the birds. However, initial productivity of birds in these habitats has been lower than expected due largely to low hatching success of early clutches. This study aims to describe behaviour associated with courtship, incubation and post-hatch care to assess possible behavioural causes of low productivity in takahe on islands. No unusual behaviour associated with breeding was observed that might result in low productivity, although only two complete copulations were observed during the study. One incomplete copulation involving a yearling male was also observed. Territorial behaviour was recorded to compare with later years when densities of island populations increase. Six territorial interactions between neighbouring pairs were observed, three when pairs were between nesting attempts and ranging widely, and three when two pairs nested in close proximity. Monitoring of aggressive behaviour may be important as it may interfere with successful reproduction.
In 1960, a census of the spotted shag (Stictocarbo punctatus punctatus) population on Banks Peninsula found 9,787 breeding pairs (Turbott & Bell 1995). Here we report the results of a comparative census conducted on Banks Peninsula during the 1996 breeding season. Thirty-six years after the original census, the number of breeding pairs was found to have more than doubled to 22,123 pairs. We speculate that the population was formerly limited by food availability and that a reduction in fishing effort around Banks Peninsula, especially in the late 1980s, may have contributed to the observed growth in the shag breeding population.
During 1995, participants in the Beach Patrol Scheme patrolled 3,498 km of the New Zealand coastline. There were 7,625 dead seabirds of 55 species recovered by patrollers. In addition, beach patrollers found 156 birds of 28 non-seabird species. Unusual finds were the third specimen of a beach-wrecked lesser frigatebird (Fregata ariel) in New Zealand and five Kermadec petrels (Pterodroma neglecta). Australasian gannets (Morus serrator) wrecked in larger numbers than in any year since the start of the Beach Patrol Scheme. There were 648 birds recovered at an average rate of 22.2 birds per 100 km. A large wreck of sooty shearwaters (Puffinus griseus) occurred on Stewart Island in May 1995. Causes of seabird mortality are discussed in the paper.
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.
During 1994, participants in the Beach Patrol Scheme patrolled 3253 km of the New Zealand coastline. 5477 dead seabirds of 55 species, plus 121 individuals of 25 non-seabird species were found. Unusual finds were the first New Zealand record of a Newell’s shearwater (Puffinus newelli), one soft-plumaged petrel (Pterodroma mollis) and one eastern little tern (Sterna albifrons sinensis). Large numbers of Kerguelen petrels (Lugensa brevirostris), flesh-footed shearwaters (Puffinus carneipes) and Buller’s mollymawks (Diomedea bulleri) were beach-cast in 1994. Fisheries-related mortality was identified for some seabirds found on beach patrols.
The saddleback (Philesturnus carunculatus) is now confined to New Zealand offshore islands free of the introduced carnivorous mammals, i.e. rats, feral cats and mustelids, which are assumed to have exterminated the species on the mainland during the last century. The North Island saddleback (Philesturnus carunculatus rufusater) coexists with the Polynesian rat (Rattus exulans) while the South Island saddleback (P c. carunculatus) thrives only on rat-free islands. An experimental transfer to Kapiti Island, where Norway (R. norvegicus) and Polynesian rats occur, provided an opportunity to test the hypothesis that North Island saddlebacks could coexist with both rat species. I compared the survival of saddlebacks on Kapiti Island with that on Cuvier and Little Barrier Islands where the only rodent is R. exulans. On Kapiti Island, saddlebacks suffered high mortality, and despite high productivity, there was insufficient recruitment of young to balance losses of adults. Significantly more nests sited less than one metre above the ground were preyed on by rats on Kapiti Island than on Cuvier and Little Barrier Islands. Saddlebacks on Kapiti Island which roosted in high or secure cavities survived longer than those birds which roosted in low or vulnerable places. These observations are consistent with the ground-foraging and predatory behaviour of R. norvegicus. On Kapiti Island, 21 rat-killed birds were found at nests and roosts, whereas no rat-killed birds were found at nests and roosts on Cuvier and Little Barrier Islands, although the contents of some nests were preyed on by R. exulans. On Kapiti Island, R. norvegicus faeces were found with the remains of several dead birds, providing direct evidence that this rat was the predator. The poor survival and recruitment of saddlebacks on Kapiti Island, coupled with observations of rat-killed birds and plundered nests near the ground, suggest that saddlebacks are unable to coexist with both rat species, and that R. norvegicus is probably an important predator. The cavity nesting and roosting habits of the saddleback make this species especially vulnerable to mammalian predators.