No abstract

Beak and feather disease virus (BFDV) infections are often fatal to both captive and wild parrot populations. Its recent discovery in a wild population of native red-fronted parakeets has raised concerns for the conservation of native parrots, all of which are threatened or endangered. The question of a recent introduction versus a native genotype of the virus poses different conservation-management challenges, and thus, a clear understanding of the molecular phylogeny of BDFV is a crucial step towards integrated management planning. This study represents the first comprehensive attempt to screen New Zealand's endangered and threatened psittacines systematically for BFDV. We sampled and screened kakapos (Strigops habroptilus), kakas (Nestor meridionalis), keas (N. notabilis), Chatham parakeets (Cyanoramphus forbesi), Malherbe's parakeets (Cyanoramphus malherbi), yellow-crowned parakeets (C. auriceps) and red-fronted parakeets (Cyanoramphus novaezelandiae), as well as eastern rosellas (Platycercus eximius), an introduced species that is now common throughout the North Island, for BFDV. Out of all species and populations sampled (786 individuals), we found 16 BFDV-positive red-fronted parakeets from Little Barrier Island/Hauturu, seven eastern rosellas from the Auckland region, and eight yellow-crowned parakeets from the Eglinton Valley in the South Island. The full genomes of the viral isolates from the red-fronted parakeets share 95-97 % sequence identity to those from the invasive eastern rosellas and 92.7-93.4 % to those isolates from the South Island yellow-crowned parakeets. The yellow-crowned parakeet BFDV isolates share 92-94 % sequence identity with those from eastern rosellas. The low level of diversity among all BFDV isolates from red-fronted parakeets could suggest a more recent infection among these birds compared to the yellow-crowned parakeets, whereas the diversity in the eastern rosellas indicates a much more established infection. Pro-active screening and monitoring of BFDV infection rates in aviaries as well as in wild populations are necessary to limit the risk of transmission among threatened and endangered parrot populations in New Zealand.

Yellow-crowned parakeets (Cyanoramphus auriceps) were studied in the Eglinton Valley, Fiordland, New Zealand. Productivity and mortality were closely related to cycles of beech seeding. Following a heavy beech mast, parakeets fed extensively on beech seed, and bred not only during their normal late summer breeding season, but right through the following winter, spring, and summer. During this time, the parakeet population increased dramatically, but in the following autumn it declined sharply, probably as a result of the depletion of beech seed and high rates of predation by stoats and perhaps other arboreal predators. Nesting parakeets are very vulnerable to stoat predation because they are hole-nesters and because their chicks are very noisy just before fledging. Stoat trapping during a stoat irruption seemed to be of no benefit. Although trapping reduced stoat population density, enough stoats remained to prey on all accessible parakeet nests. More extensive trapping, and trapping when stoat numbers are relatively low, are more likely to benefit parakeets.

The mohua or yellowhead (Mohoua ochrocephala) is an endangered, hole-nesting forest bird endemic to New Zealand. Mohua suffer periodic population crashes due to severe predation by the introduced stoat (Mustela erminea). In 1990, a stoat population irruption provided an opportunity to reassess the impact of stoat predation on mohua and to test two linked hypotheses: that adaquate control of stoats by trapping is possible, and that it is a viable management option to assist mohua recovery. The primary experiment (summer 1990/91) was repeated in the summers of 1991/92 and 1992/93 when stoat numbers were lower. Mohua productivity and adult female mortality were compared in two study areas, one trapped and one untrapped, in the Eglinton Valley, Fiordland. Sixty-two stoats were caught in the 50 ha trapped area during summer 1990/91. The fledging of many first clutches, and the laying of second clutches, coincided closely with the period when high numbers of stoats were being caught in traps. Eighty percent of the nests in the trapped area fledged young, compared with only 36% in the untrapped area. Pairs produced nearly twice as many young in the trapped area. A higher proportion of breeding females disappeared from the untrapped area. In the two subsequent summers, 29 and 14 stoats were caught, and breeding success was higher Received 29 August 1995; accepted 30 April 1996 than previously recorded in both trapped and untrapped areas. We suggest that trapping in the year following a stoat irruption may also be warranted.

Three male and two female ship rats (Rattus rattus) were radio-tagged and tracked in beech (Nothofagus) forest in the Eglinton Valley, Fiordland, New Zealand over two field periods in 1996 and 2000. The home range of each animal was calculated using the minimum convex polygon method. Ranges of three male rats were 7.5, 9.1, and 11.4 ha whereas those of the female rats were 0.89 and 0.27 ha. The home ranges recorded for male rats were considerably larger than those reported from other studies in non-beech forest. Ship rats are important predators of forest birds, and home range information could be used to provide a guide for trap or bait station spacing in beech forests. To carry out rat control in beech forests effectively, further studies are needed to determine if the results of this pilot study are typical, and if home ranges of ship rats change with season, or at various stages of the beech mast cycle.