Publications Archive

  The New Zealand Threat Classification System is used to prioritise and evaluate conservation programs, as an advocacy tool for biodiversity and as a guide to risk when assessing the severity of effects of development. A lack of transparency and adherence to scientific conventions when compiling the listings for birds led to previous criticism (Williams 2009). Two recent papers provide sufficient information to independently assess the threat status ranking of two endemic birds. Both papers provide detailed information on multiple sites and assess the influence of different threats. Both also provide an estimate of population size and generation time as required for assigning a Threat Classification. The authors conclude with clear recommendations on appropriate New Zealand and IUCN threat status ranking in both papers. We consider that the authors have failed to consistently apply the criteria for assessment in the Threat Classification Manual (Townsend et al. 2008) and IUCN Red List Guidelines (IUCN 2019). We re-evaluate the recommended threat status in light of adherence to the criteria, the data used and the analysis methodology selected. We recommend greater transparency, use of additional methodology and adherence to the guidelines to improve consistency and reliability of threat status classification.  

  In October 2019, an expedition to the subantarctic Bounty Islands provided the opportunity to conduct comprehensive ground counts of erect-crested penguins to assess population size and compare numbers to previous surveys. The entirety of Proclamation Island, an erect-crested penguins’ stronghold, was surveyed and number of active penguin nests was determined via ground counts. Drone surveys aiming at assessing seal numbers, provided high- resolution aerial photography allowing spatial analysis of penguin nest densities on four islands, i.e. Proclamation, Tunnel, Spider, and Ranfurly Islands. A total of 2,867 penguin nests were counted on Proclamation Island between 24 and 29 October. Adjusting for the earlier timing of the survey compared to counts conducted since 1997, nest numbers were only marginally lower (~2.4%) than in 1997 and 2004 suggesting that the penguin population has remained stable for the past 20 years; a ~10% reduction in penguin numbers in 2011 seems to be related to warmer than average ocean temperatures that year. Density analysis from drone imagery showed highly heterogenous distribution of penguin nests, with birds preferring areas sheltered from prevailing south-westerly winds. This also means that a previous estimate from 1978 which relied on uniform extrapolation of nest densities to what was assumed to suitable breeding areas substantially overestimated the true population size, thereby contributing to the species current ‘endangered’ threat ranking.  

  Nesting outcomes of Canada geese (Branta canadensis maxima) in Canterbury, New Zealand were recorded from a sedentary population nesting at coastal Lake Forsyth (1967–70) and from a seasonally migratory population nesting in headwater valleys of the Waimakariri River (1966–80). Mean clutch size in 462 Lake Forsyth nests was 5.3 (sd = 1.3) eggs, with clutches of 4, 5, and 6 eggs comprising 17%, 30% and 30% respectively of the total. Goslings hatched from 67.4% of 1,602 eggs in 298 monitored nests, and the entire clutch hatched successfully in 42.6% of the monitored nests. Mean productivity at hatching was 3.6 (sd = 2.3) goslings per nest. Mean clutch size in 1,211 Waimakariri River headwaters nests was 4.5 (sd = 1.3), with clutches of 4, 5, and 6 eggs comprising 25%, 32%, and 20% respectively of the total. Goslings hatched from 63.3% of 3,952 eggs in 871 monitored nests, and the entire clutch hatched successfully in 30.5% of the monitored nests. Mean productivity at hatching was 2.9 (sd = 1.9) goslings per nest. Relative to Canada geese in their native North American range, geese nesting at Lake Forsyth laid clutches of similar size, had similar hatching success but higher nest success whereas geese nesting in the Waimakariri River headwaters laid, on average, conspicuously smaller clutches, had similar hatching success, but higher nest success.  

  Aggressive interactions among species competing for resources are common and usually asymmetric, leading to consistent dominance hierarchies. Here, we document aggressive interactions among six albatross and three petrel species off southern New Zealand, in response to supplemental food provided by ecotourism boats. For species with sufficient sampling, we found a consistent dominance hierarchy, with Diomedea antipodensis gibsoni > D. epomophora > Macronectes halli > Thalassarche cauta > T. salvini > T. bulleri > Daption capense. The heavier species was dominant in most species pairs. Dominant species monopolised the food provided by displacing subordinates. However, subordinate species appeared to gain access to some food through fast responses, greater manoeuvrability, and feeding on small pieces of food ignored by dominants. Similar congregations and interactions at natural food sources suggest that dominance hierarchies may play an important role in structuring the diverse seabird communities in the southern oceans.  

  Swiftlets (Collocalia, Aerodramus) make up a guild of birds which prey on a wide range of aerial insects and spiders. The studies reviewed here show their prey to include 19 orders and 55 families of insects plus spiders. Most swiftlets seem to take whatever is available at the time and place, with site to site and year to year differences noted. One species (black-nest swiftlet) appears to be a swarm-feeding specialist. Prey size ranged from

  Understanding how animal behaviours are affected by external factors such as time of day/year and weather conditions is fundamental to understanding the basic biology of a species and can thus help with conservation management. Weka (Gallirallus australis) is typically crepuscular in its habits, but there is some evidence to suggest that it can also be nocturnal. We conducted a longitudinal study of the nocturnal habits of the western weka (G. australis australis) located at Manaroa in New Zealand’s Marlborough Sounds. We used model selection information criterion to examine how the numbers of weka in an open environment (lawn) changed with time of night and season, as well as differing weather and moonlight conditions. In addition, we undertook night-time behavioural observations during a four-month subset of the study period. Numbers of weka declined through the night and increased non-linearly around dawn. Weka were more likely to be present during moonlit nights and at warmer temperatures during the evening. There was considerable seasonal variation, with the highest number of weka during autumn and lowest during summer. Behavioural observations demonstrated that weka were active throughout the night, with foraging being the most frequently-observed behaviour.