Publications Archive

  This paper presents the results of four censuses of the northern New Zealand dotterel population undertaken between 1989 and 2011. During that period, the population increased by roughly 50%, from about 1,320 to about 2,130 birds. Most birds (85%) were in the northern part of the North Island (Northland, Auckland, and Coromandel Peninsula), but the taxon is expanding its range southwards on both the west and east coasts. On the east coast, a few pairs are now breeding close to Cook Strait. Population trends varied between regions, and almost all of the overall increase was a result of increases on the east coast. The highest rates of increase were on the Auckland east coast and on Coromandel Peninsula, probably because the intensity of management has been highest in those regions. In the Auckland urban area, birds now routinely breed inland, mainly on grass or bare earth; elsewhere, the taxon is almost entirely coastal. The proportion of birds on the west coast has fallen over the past 50 years, and about 85% of the taxon is now found on the east coast. If the overall increase in numbers has continued at the same rate since 2011, there would be about 2,600 birds in 2020. The size of the population and its rate of increase justify the recent down-listing of the subspecies to a threat ranking of At Risk (Recovering), but it remains Conservation Dependent. The recovery programme has been highly successful, and most management of the taxon is now undertaken by community groups, regional councils, and volunteers. Continuing threats include predation, flooding of nests, and disturbance during breeding; in future, continuing coastal development and increased recreational activity will probably degrade habitat further, particularly on the east coast, and climate change will have a range of impacts.  

  During southward migration from Alaska in 2006, a satellite-tracked female bar-tailed godwit (Limosa lapponica baueri) encountered adverse weather and stayed between 19 September and about 28 September 2006 at Ouvéa (Loyalty Islands, New Caledonia), where she apparently died. Ouvéa was visited between 27 September and 7 October 2007 to look for godwits. A total of eight godwits was recorded of which one, thought to be an adult female, may have been a dropout migrant. The remaining birds appeared to be immatures.  

  We undertook a survey of coastal wetlands in Canterbury (NZ) during a widespread river flooding event in Spring 2013 to quantify numbers and distribution of wrybill (Anarhynchus frontalis). We found 740 birds, of which 685 (92.6%) were at Lake Ellesmere/Te Waihora. We calculate that 15.8% of the estimated effective wrybill breeding population were displaced from breeding rivers by floods at this time. Our findings support the evaluation by Dowding & Moore (2006) that the network of wetlands along the Canterbury coast appears to be of critical importance to wrybill as breeding season flood refugia.  

  We analysed standardised estimates of local occupancy probability of 13 species of native wading birds, terns and gulls (order Charadriiformes) derived from the New Zealand Ornithological Society’s national Atlas of Bird Distribution collated in 1969–1979 and 1999–2004. We show systematic patterns in changes with taxonomic level of endemism, breeding habitat (coastal or inland), and location (distance from the coast, road density, and degree of land development for agriculture and forestry). The main changes were decreases in endemic inland breeding species within their inland South Island breeding ranges, and increases in most coastal-breeding species and some inland-breeding species around much of the coast, especially near urban centres in the North Island. Our results are consistent with both intensive land use and predation contributing to widespread declines of inland-breeding species across inland South Island. Potential causes of occupancy changes around the coast are less clear, and we offer some suggestions.  

  Co-ordinated counts of waders across New Zealand have been undertaken in November and June since 1983; the consistent timing of counts aimed to reduce variation from the effect of seasonal changes in bird numbers. The Australian Shorebird census and the wider Asian Waterbird Census, however, are conducted in January, making direct comparison with the New Zealand counts potentially problematic, especially if an attempt is to be made to assess total flyway populations. Since 1998 waders on Farewell Spit (40°30.5 ́S, 172°45 ́E to 40°33.5 ́N 173°02 ́E) have been counted in February as well as in November and June. Counts of bar-tailed godwit and ruddy turnstone were on average 20% and 35% higher in February compared to November, respectively. Also, counts of the endemic migratory South Island pied oystercatcher were 15% higher in February compared to June. The improvement of data for overall population assessments is not only important for establishing trends of species but is also important for applying the 1% population criterion for wader site assessments.  

  The wrybill (Anarhynchus frontalis) is an endemic plover that breeds only in braided rivers east of the main divide in the South Island of New Zealand. It is threatened by a range of factors, including loss and degradation of habitat, flooding, and predation. We monitored wrybills in 2 sites in the Tekapo River and 2 in the Tasman River in the Mackenzie Basin, South Canterbury, during 3 breeding seasons (1997/98–1999/2000). We aimed to compare survival and productivity between areas with and without trapping (mammalian predator control) to determine whether predator control was associated with higher survival and/or breeding success of wrybills. In the Tekapo River, results were similar between trapped and un-trapped areas, suggesting that control had little effect. In the Tasman River, there were large differences between the two sites and trapping appeared to be beneficial; in the upper river (un-trapped), productivity and survival were very low and in the lower (trapped) site they were high. Over the whole study, 67.3% of nests hatched, and depredation was the largest cause of nest failure. Fledging success (the proportion of chicks hatched that fledged) averaged 35.4%. Losses at the chick stage were higher than at the egg stage, and there was only a weak correlation between nesting success and overall breeding success; we therefore caution against the use of nesting success as a proxy for overall breeding success. Productivity averaged 0.49 chicks fledged per pair over the whole study; when the very low values from the upper Tasman site were excluded, productivity averaged 0.61. Survival of adult male wrybills was lower than survival of females in all four study sites. Measurement of adult survival is important in determining the full effect of predator control (and in determining population trends) but is often overlooked. At the time of our study, wrybill populations in 3 of our 4 study sites appeared not to be self-sustaining and, in the absence of immigration, were in decline. A number of factors, including depredation by mammals, can affect breeding success. Trapping may be beneficial, but temporal and geographic differences in predator densities, as well as variability in other threats (such as flooding and levels of avian predation) mean that predicting when and where mammalian predator control may benefit wrybills is currently difficult.  

  Bar-tailed godwits (Limosa lapponica) were counted throughout New Zealand and on the east coast of Australia during the 2019–2020 austral summer, in the first attempt to assess the total population of the subspecies baueri on the southern hemisphere non-breeding grounds. Survey coverage in New Zealand was nationwide (158 sites surveyed); surveys in Australia covered 314 sites between Great Sandy Strait in southern Queensland, and the Gulf St Vincent in South Australia. Areas north of Great Sandy Strait were either partially counted or were not visited over this survey period. Partial surveys were excluded from the survey results. The total number of godwits counted was 116,446. If allowance is made for an additional ~10,000 birds expected to have been present in northern Queensland (based on previous surveys), the total population of baueri in New Zealand and Australia would have been about 126,000. The 2019 breeding season was very successful, with the highest recorded number of juvenile birds since 2011 and 2012.  

  Banded dotterels (tūturiwhatu, Charadrius bicinctus bicinctus) are small plovers inhabiting New Zealand’s braided rivers, estuaries, seashores, and open country. They are considered Nationally Vulnerable under national threat listing criteria, but with uncertainty around the trend estimation. We collated and reviewed counts of banded dotterels on their braided river breeding grounds from throughout the country, 1962–2017, to describe their distribution, assess population trends, estimate rates of population change, and assess the appropriateness of the threat status given to this species. We also used nationwide winter count data for banded dotterels from 1984 to 2018 as an independent measure to compare trends. Banded dotterel counts were recorded for 119 braided and shingle river reaches, mostly in the South Island (87%) with far fewer rivers in the North Island (13%). The sum of banded dotterel counts was 12,730 birds when tallying the most recent counts/river. Although they were most widespread in the South Island, particularly Canterbury, the majority (>50%) of dotterels counted on the most recent surveys were from just 10 (8%) rivers with the largest single concentrations on three Hawkes Bay rivers. Counts suitable for long-term trend analysis were only available for South Island sites. Widespread declines in banded dotterel count indices were recorded. The weighted mean annual rate of change across 33 South Island rivers was -3.7% p.a. (per annum), which equates to a 52.3% decline over 20 years (~3 generations). We also detected a negative trend in dotterel numbers based on national winter count data, but of a smaller magnitude (-1.4% p.a., equating to a 25% decline over 20 years). However, trends in Australia, where c. 60% of banded dotterels over-winter, are unknown. In contrast, a significant population increase was measured on the Hakatere Reach of the South Ashburton River, which has intensive, sustained predator control, and several predator trapping initiatives on other braided rivers and coastal areas indicate declines can be reversed with management if applied at an extensive landscape scale. Banded dotterels are subject to a wide range of threats including very high levels of predation by invasive predators, human disturbance on breeding grounds, and habitat loss and degradation. Using the precautionary principle, the rates of decline on South Island braided rivers confirm the classification of Nationally Vulnerable using the NZ Threat Classification system. However, results suggest that the IUCN threat status for banded dotterel should be reclassified from Least Concern to Endangered.  

  The results of biannual national wader counts done during winter (June–July) and early summer (November– December) by the Ornithological Society of New Zealand (OSNZ)/Birds New Zealand from 2005 to 2019 are compared with similar counts done in 1983 to 1994. Although the national wader counts continued 1995–2004 the coverage was insufficient to enable comparable analyses; however, reference is made to some sites that were counted continuously since 1983. At least 1,567 counts at 74 sites nationally resulted in 3,977,228 waders of 39 species being counted. The numbers of most species have declined since the 1983–1994 surveys, particularly evident in the northern hemisphere migrants, with the numbers of some species down by 50% or more. Such changes in numbers are likely to be a true reflection of the declining populations rather than changes in the counting effort. Some native species are faring better, mostly as a result of numerous community-led wader protection projects for northern New Zealand dotterels (Charadrius obscurus aquilonius) and variable oystercatchers (Haematopus unicolor).  

  Many species recovery programmes use pedigrees to understand the genetic ancestry of individuals to inform conservation management. However, incorrect parentage assignment may limit the accuracy of these pedigrees and subsequent management decisions. This is especially relevant for pedigrees that include wild individuals, where misassignment may not only be attributed to human error, but also promiscuity (i.e. extra-pair parentage) or egg-dumping (i.e. brood parasitism). Here, we evaluate pedigree accuracy in the socially monogamous and critically endangered kakī (black stilt, Himantopus novaezelandiae) using microsatellite allele-exclusion analyses for 56 wild family groups across three breeding seasons (2014–2016, n = 340). We identified 16 offspring where parentage was incorrectly assigned, representing 5.9% of all offspring. Of the 16 misassigned offspring, three can be attributed to non-kakī brood parasitism, one can be assigned to human error, but others cannot be readily distinguished between non-monogamous mating behaviours and human error. In the short term, we advise the continued use of microsatellites to identify misassigned offspring in the kakī pedigree, and to verify non-kakī brood parasitism. We also recommend the Department of Conservation’s Kakī Recovery Programme further evaluate the implications of pedigree error to the management of this critically endangered taonga species.  

  Ruddy turnstone (Arenaria interpres) is the third most numerous Arctic-breeding wader that occurs in New Zealand. Numbers of turnstones in New Zealand have declined but identification of potential causal factors is hampered by lack of information of the migration routes used. Re-sights of marked birds indicate that some New Zealand turnstones pass through East Asia and Australia on both northward and southward migration. Information on possible migration through the Pacific is lacking.  

  The foraging behaviour of two foliage gleaning birds, rifleman and grey warbler (henceforth warbler), was studied at Kowhai bush, Kaikoura, with the aims of exploring behavioural variation by individual pairs, and broader patterns of foraging behaviour for each species. Data on six foraging variables were collected from individually identifiable birds of known breeding status at the time of sampling. A total of 1,632 samples were taken during the spring/summer period of 1987/8. Data analysis explored foraging behaviour in relation to species, sex, and breeding stage. Individual pairs of riflemen exhibited significant variation in behaviour, indicating behavioural specialisation that I term a “foraging personality” identified as an emergent characteristic of each pair. Riflemen showed greater within-pair variation than warblers. The similarities and differences in foraging behaviour between the two species are described and are linked to their behavioural ecology. Analyses are presented in relation to the problem of data independence when repeated samples are taken from one individual.