Mohua (Mohoua ochrocephala) are endemic to the South Island of New Zealand but they have declined in both range and abundance. The causes of decline include predation from introduced predators and forest clearance. Mohua have survived in reasonable numbers in the Dart Valley in west Otago. In this paper we describe the relationship between the presence of mohua breeding territories and vegetation at a 1 ha scale within low altitude, red beech-dominated forest. The extent of shrub or regeneration was found to have the strongest association with the presence/absence of breeding mohua. Other factors which increase leaf volume, such as forest-edge and broken canopy were also important in explaining the presence of mohua. Milling was found to have a long lasting negative impact (>70 years) on mohua presence. Management which reduces grazing and increases the shrub and regeneration forest component is likely to increase mohua carrying capacity.
An annotated checklist of birds recorded or reported on the Aleipata Is, Samoa is presented. Nu’utele and Nu’ulua Is were the focus of an attempt to eradicate Pacific rats (Rattus exulans) in 2009. The data presented are from bird surveys intended to provide baseline information to determine the effect of rodent eradication on the bird fauna. Fanuatapu or Namu’a Is were surveyed as experimental controls. A total of 42 species were recorded or reported, comprised of 24 species of land birds (including 3 introduced species) and 18 species of seabirds and shorebirds. Morphometric data are also presented from Friendly ground-doves (Gallicolumba stairi) that were removed from Nu’utele I and held in captivity during the rat eradication attempt.
Information on the relevant spatial scale for controlling pest birds causing significant crop damage is generally lacking. Here, we assess the potential of 2 radiotracking systems (hand-held vs. elevated twin-Yagi antennae) for monitoring pest bird ranging behaviour on and around an arable farm. Radio-transmitters were fitted to 19 European greenfinches (Carduelis chloris) in the summer and 25 house sparrows (Passer domesticus) in the winter. Greenfinches were most likely to be detected in or near Brassica seed crops, particularly on the study farm, but 12% travelled large distances (>3 km) between Brassica crops in the landscape. Even though house sparrow home ranges were widely dispersed across the landscape, most overlapped with the farm boundary and were positively associated with woody vegetation. Relative to hand-held antennae, the elevated twin-Yagi system increased the detection radius for tagged birds from 100 m to 2000 m and also the number of location data, albeit over a more restricted area.
Orange-fronted parakeets (Cyanoramphus malherbi) are New Zealand’s rarest parakeet species with a global population of less than 500 individuals on remnant mainland populations and reintroduced populations on offshore islands. Since there is limited information about habitat preferences by this species on offshore islands I characterised habitat use on Maud Island, where captive-bred parakeets were introduced in 2007. I compared the vegetation characteristics of 29 plots (each 25 m2) where parakeets were encountered and 23 plots randomly selected. Parakeets were observed foraging in 96.6% of the plots. Plots used by parakeets showed significantly higher density of stems under 20 cm dbh and a higher canopy than random plots. Used plots also tended to have greater canopy cover and lower understory and ground vegetation covers. These results indicate that orange-fronted parakeets use ecotones of broadleaf coastal forest-manuka scrub, and pine plantations-manuka scrub for foraging highlighting the potential value of islands with mixed patches of these vegetation types as future refuges for this critically endangered species.
Population size and breeding success of northern New Zealand dotterels (Charadrius obscurus aquilonius) were studied on the recently mammalian predator-eradicated Motuihe Island in the Hauraki Gulf, New Zealand. The island’s entire breeding population was monitored during the austral breeding season from Nov 2007 – Feb 2008. Nine breeding pairs were identified and their breeding success recorded. A total of 41% of nesting attempts produced fledglings and 1.22 chicks fledged per pair for the season; each egg had a 38% chance of survival to fledging. The breeding success of this endemic shorebird was twice as high on Motuihe Island as that at unmanaged mainland sites, and is comparable to levels of breeding success at other managed sites with mammal trapping or predator-proof fencing. The only identified cause of nesting failure over the breeding season was avian predation. Suggestions are made to maintain and enhance breeding success at this locality.
Biometric studies of short-tailed shearwaters (Puffinus tenuirostris) indicate differences in body mass and linear measurements between sexes. Here the degree of sexual size dimorphism in 390 short-tailed shearwater adults is assessed and a sex-discriminating function is produced to improve methods for sexing live birds in the field. Analysis of body mass and linear measurements showed males to be significantly heavier and larger than female birds in all variables. The largest degree of sexual size dimorphism was in bill depth (7.5%) followed by body mass (5.1%). Bill depth plus total head length were the most accurate variables in a discriminant function model. Together, these 2 variables predicted sex with 84% accuracy. Bill depth alone predicted sex with 82% accuracy. However, application of a sex-discriminating model developed from another colony, did not correctly classify the sex of adult birds as accurately. This can be explained by the existence of significant geographical variation in body size within the species and reinforces the need for colony-specific sex discriminant models. Comparisons within-pairs revealed that bill depth is a more reliable indicator of sex, without the need for a discriminant function analysis. Contrary to previous studies, measurements of male and female partners showed no evidence of assortative mating in any character assessed. If short-tailed shearwaters mate assortatively then it may be based on traits other than structural size.