The black petrel (Procellaria parkinsoni) is recognised as the seabird species at greatest risk from commercial fishing activity within New Zealand fisheries waters. Despite the fact that valuable mitigation information could be obtained from such data, little is known about the diving ability of this species. Diving data were obtained from electronic time–depth recorders from 22 black petrels breeding on Great Barrier Island (Aotea), Hauraki Gulf, New Zealand, during the early chick rearing period from January-February in both 2013 and 2014. This paper presents the first information on the diving ability of black petrels. The deepest dive recorded was 34.3 m, but maximum dive depths varied considerably among individuals (range 0.8-34.3 m). The majority (86.8%) of all dives were < 5 m and black petrels rarely dived to depths of >10 m. The majority (92.7%) of dives were during the day and time of day had no major effect on dive depth. Only males dived at night, between 2300 and 0200 hours. This information could be used to improve mitigation measures for black petrel and other seabird bycatch in longline fisheries particularly in relation to recommended depths for unprotected hooks and line sink rates. To achieve the recommended minimum 10 m depth for unprotected hooks it has been shown that hooks have to be deployed at 6 knots with a 0.3 m/second line sink rate when using 100 m streamer lines. Adoption of these measures should further reduce black petrel bycatch in longline fisheries.
Many bird species have been successfully introduced beyond their natural range, some becoming more abundant in their new environment than in their country of origin. In this study, bird density was measured at 2 study areas comprising a total of 48 recreational parks in northern England and Canterbury, New Zealand, for 10 focal species (native to the former, introduced to the latter). Site characteristics and presence of other bird species were also recorded and investigated as potential explanatory factors for differences in density between the 2 study areas. Common redpoll, common starling, European greenfinch and house sparrow had significantly higher densities at the New Zealand sites. Analysis using generalised linear models revealed a negative relationship between common starling density and proportion cover of trees and shrubs, and a positive relationship between common redpoll, common starling and European greenfinch densities and site species richness. However, since there were no significant differences in site characteristics or site species richness between study areas, these relationships could not account for higher densities at the New Zealand sites. There was an apparent negative relationship between densities of common starling and house sparrow and foraging guild diversity, suggesting that interspecific competition may contribute to differences in density between study areas. The proportion of variation explained by the models was relatively low, suggesting that there may have been missing variables that influenced species density. More detailed study of a wider range of variables is required to investigate this further.
Nocturnal surveys for collared petrel (Pterodroma brevipes) indicate significant variation in the number of birds reported by site, time of year, and survey method. Collared petrels were recorded at 3 new islands within Fiji in 2011. These records indicate that locating collared petrels requires focussed survey effort, although they do not definitively confirm breeding on the islands, for which ground-based searches would be required. When visiting sites where there has been no recent evidence of collared petrel breeding, surveys should be undertaken between February and April (at the start of the breeding season), should use an active method of survey comprising both light for attraction and playback and/or with ‘war whooping’, and should be repeated at a number of sites before concluding that an island holds no breeding birds.
Orange-fronted (Cyanoramphus malherbi) and yellow-crowned parakeets (C. auriceps) are sympatric congeners that are secondary cavity nesting species, with the former being critically endangered. Both currently inhabit anthropogenically-modified Nothofagus forest. We compared the characteristics of nest sites in both species and found the majority of nest site parameters (tree height, height of hole above ground, DBH, tree condition and aspect) were similar. However, orange-fronted parakeets selected nest cavities with a significantly narrower entrance, and when situated in red beech (Nothofagus fusca), nest entrances were significantly smaller in area than in yellow-crowned parakeets. As the male orange-fronted parakeet is smaller in body mass than the male yellow-crowned parakeet (only males feed nestlings when laying multiple clutches), the difference in nest hole size may simply indicate that they are capable of utilising smaller entrances. We also found that orange-fronted parakeets selected nest holes in standing dead trees more frequently and nest sites in silver beech (N. menziesii) less frequently than expected. While the lack of differences in nest site characteristics suggests some interspecific competition may be occurring between these species (i.e., they occasionally use the same nest holes), it is difficult to establish this experimentally and to determine whether these differences are artefacts of former niche separation in unmodified forest.
A 15,000 ha low-intensity stoat (Mustela erminea) trapping network was established in the Murchison Mountains in 2002, primarily to protect the last natural population of the critically endangered takahe (Porphyrio hochstetteri). We compared the productivity and survival of threatened southern brown kiwi or tokoeka (Apteryx australis) living in 3 valleys that were covered by this trapping network with those in a nearby valley that was left untreated. Chick survival to 6 months old was significantly higher in the trapped areas (37%) than in the untrapped area (19%). This doubling of chick survival was sufficient to change the rate of population growth, as derived from Leslie matrix analyses, from a projected decline of 1.6% per annum without management to a projected increase of 1.2% per annum with trapping.
Prior to 1992 the total population of New Zealand king shag (Leucocarbo carunculatus) was estimated to be about 300 individuals. Between 1992 and 2002, colonies in the outer Marlborough Sounds, New Zealand were surveyed by boat and the total population was estimated to be 645 birds. About 92% of all birds occurred at Duffers Reef, North Trio Island, Sentinel Rock, and White Rocks, with an estimated 102-126 breeding pairs. A survey in February 2015 was the first to be conducted from the air. All colonies were photographed within 44 minutes prior to the morning departure and the total population was estimated to be 839 individuals. A total of 187 pairs/nests were recorded using aerial 3D images of all breeding colonies in June 2015. North Trio Island was the largest breeding colony with 33.7% of all nests, followed by Duffers Reef with 18.7% of all nests. Despite the larger revised population size, the species remains Nationally Endangered.
The white-flippered penguin (Eudyptula minor albosignata) population on Banks Peninsula, New Zealand, was extensively preyed on by mammalian predators during the 1980s and 1990s with the loss of many colonies and the reduction in size of others. This paper presents the results of a 20-year study designed to identify the predators primarily responsible for these losses. It was based on the monitoring of 9 colonies ranging in size from 2 to 37 nests on a 1.7 km section of rocky coastline. Predators were trapped in the largest colony to determine the species present and their relevant behaviour. The other colonies were left unprotected, 6 of which were accessible to predators and 2 were not. Predation of penguins was first observed in the area in 1981 and it occurred annually through to the end of the study in 1995. Five of the 6 unprotected colonies were lost in 1982 and 1983 while the inaccessible colonies were unaffected. The remains of penguins that had been preyed on were found in the ‘protected’ colony in 11 of the 15 years between 1981 and 1995. These had been taken during the second half of the moulting season in February, and during the non-breeding season from April to August. No predation was observed during September to January when the penguins were breeding. A total of 47 mustelids were trapped in the ‘protected’ colony of which 43 (91%) were ferrets (Mustela furo). Overall there were 16 instances of predation that could be attributed to ferrets and 1 that was attributed to a ferret although the predator was not caught. The onset and sustained period of penguin predation by ferrets followed an eruption in their numbers Banks Peninsula-wide. This was most likely triggered by a corresponding increase in the numbers of rabbits (Oryctolagus c. cuniculus), their primary prey.