Publications Archive

Reports of dispersal by juvenile weka (Gallirallus australis greyi) on the North Island are rare. Estimates of the distance dispersed and the rate of survival of dispersers are important factors to be considered for weka conservation. I captured 20 young weka during a 2-year study and attached radio transmitters to 4 of them. In addition, I was able to measure the distance travelled by 3 banded weka that were either recaptured or seen again, and 1 weka that was recovered dead. Newly independent weka used a part of their parental home range at first, then moved up to 3.5 km. Two-stage dispersal, where young weka leave their parents but remain close by and move away later, has been reported on offshore islands: my results are consistent with that type of dispersal. More research is needed on weka dispersal because it is likely to be linked to factors important for their conservation and management.

A species of small procellariid known locally as titi, probably the black-winged petrel (Pterodroma nigripennis), nested into the historic period in burrows in the volcanic soil of the uplands of Mangaia in the southern Cook Group. The demise of this titi as a breeding bird on Mangaia was probably caused by a combination of the detrimental effects of human harvesting and various introduced mammalian predators which were present on Mangaia after the arrival of missionaries in the early nineteenth century.

The Chatham Island pigeon or parea (Hemiphaga chathamensis) is an endangered species of pigeon endemic to the Chatham Islands. Effective conservation management of the Chatham Island pigeon required an understanding of its ecology and identification of the causes of decline. We studied the pigeon in their last remaining stronghold; the south-west of Chatham Island, New Zealand, between July 1991 and December 1994. We describe the nesting behav- iour, nesting success, and the dispersal, survival, and recruitment of juveniles. The study was confounded by the lack of information on predator numbers or outcomes of pigeon nests from before the start of predator control activities within and adjacent to our study area. Despite a previously reported decline in pigeon numbers up until the early 1990s, during this study there was a 3-fold population increase, and only a low level of predation by possums and rats. Other than predation, no factor which might previously have limited the pigeon population was identified. We assume that the trapping and poisoning of pest-mammals since 1989, has been sufficient to allow the population of Chatham Island pigeon to recover.

The chick-rearing strategy of yellow-eyed penguins (Megadyptes antipodes) breeding on Otago Peninsula was examined in 12 pairs of adults, between 17 November 1996 and 3 1 March 1997, from time of hatching of chicks to parental moult. Differences in behaviour of both male and female parents towards one- or two-chick broods were not statistically significant, but behaviour towards all offspring changed significantly over time with respect to breeding phases. Differences observed resulted from a change in feeding procedure. “Food-walks” started significantly earlier in the course of a feeding session as time progressed, while major components (duration and number of individual feeds) decreased significantly. The changes observed are interpreted as resulting from the chicks’ growing independence in concert with the parents’ decreasing urge to spend time with their offspring outside the still necessary feeding encounters. An evolutionarily stable environment and reliable food source are suggested as the reason for the lack of development of different chick-rearing strategies for different numbers of offspring or for male and female breeders.