Many New Zealand forest bird species have poor flying ability, limiting their ability to recolonise vacant habitat, and restricting gene flow between populations separated by water. Three endemic passerines considered to have poor dispersal ability have been reintroduced to 3 islands in Dusky Sound where stoats (Mustela erminea) have been eradicated: South Island robins (kakaruwai, Petroica australis) to Anchor Island (1,137 ha), Indian Island (168 ha) and Pigeon Island (73 ha), mohua (yellowhead, Mohoua ochrocephala) to Anchor and Pigeon Islands, and South Island saddleback (tīeke, Philesturnus carunculatus) to Anchor Island only. Mohua have also been reintroduced to nearby Resolution Island (20,887 ha), where stoats are controlled to low density. Stoat traps set on numerous ‘stepping stone’ islands around and between these 4 islands have created a network of predator-free habitat at varying distances from the reintroduction sites. We recorded sightings of these species during landings on 56 islands in Dusky Sound in November 2016. South Island robins had the greatest dispersal ability of the 3 species, and were found on 33 additional islands up to 1.4 km from the nearest potential source population. In contrast, mohua and South Island saddlebacks had each crossed a single water gap only, of 90 m and 100 m respectively. One or more of these 3 species have been translocated to more than 40 islands and a few mainland sites around the South Island and Stewart Island. Information on their dispersal ability across water could guide decisions on whether further translocations are necessary, both in respect to whether birds are likely to colonise nearby islands or forest patches unassisted, and in order to manage gene flow within dispersed metapopulations. South Island robins have apparently displaced tomtits (Petroica macrocephala) on at least 9 small islands in Dusky Sound.
Breeding success of the endemic black-fronted tern (Chlidonias albostriatus) and the identity of predators was studied in the upper Clarence and Acheron Rivers (Molesworth Recreation Reserve), South Island, New Zealand in the 2012, 2013 and 2014 breeding seasons. The catchment supports a nationally and therefore internationally significant population of over 720 breeding birds. A combined total of 1,510 nests were monitored over 3 seasons. Breeding success was poor with only 42.7% of nests hatching at least 1 egg, and average productivity of only 0.13 chicks fledged/nest. Breeding success varied between years and rivers, primarily due to differing predation rates. Predation and nest abandonment following nocturnal predator disturbance were the primary causes of nest failure. A total of 110 filmed predation events at nests identified ferret (Mustela furo), feral cat (Felis catus) and hedgehog (Erinaceus europaeus) as the main predators. Following a beech and tussock masting event, predation by ship rats (Rattus rattus) was significant in 2014. This is the first time predator increases following mast seeding has been shown to impact braided river birds. In contrast, avian predation was low and varied across rivers. Productivity was higher in large colonies (>25 nests) than small colonies, and in early colonies (colony formation before 31 October). A management programme to improve black-fronted tern productivity has been initiated given the national importance of this population, the ease of access to these colonies, and the identification of the invasive predators responsible for current levels of poor breeding success.
The risk of disorientation by artificial lights and subsequent ‘fallout’ has become a widely recognised issue for nocturnal procellariiform species. Using data from community-based rescue campaigns and systematic research, we assessed the characteristics of fallout events observed in fledglings of the threatened New Zealand endemic Hutton’s shearwater (Puffinus huttoni) or Kaikōura tītī. Despite strong annual variation in observed fallout numbers, the proportion of annually produced fledglings collected as ‘fallout birds’ remained below 1% each year. Among those, more than 80% survived due to community rescue efforts. Fallout was found to increase significantly during new moon, while weather effects remained inconclusive. Most fallout occurred within brightly lit areas of Kaikōura township, particularly along its coastal roads. High light source densities and high wattage lights appeared to be influential in some areas but could only partly explain the spatial distribution of fallout at this small scale.
A total of 49 breeding colonies of 3 petrel species was found on 44 of 56 islands surveyed in Dusky Sound, Fiordland National Park, New Zealand, in November 2016. Sooty shearwater (Puffinus griseus) was the most widespread and abundant species, with an estimated 21,400 burrows on 35 islands. Mottled petrels (Pterodroma inexpectata) were breeding on 12 islands (5500 burrows estimated), and broad-billed prions (Pachyptila vittata) on 2 islands (560 burrows estimated). Sooty shearwaters were found breeding among mottled petrels on 4 islands, and among broad-billed prions on 1 island. This is a 5-fold increase in the number of petrel colonies in Dusky Sound identified in published accounts, and the first estimate of the number of burrows on each island. Long-term survival of most or all of these colonies is dependent on ongoing control of stoats (Mustela erminea) in Dusky Sound. However, we suggest that islands too small to support a resident stoat population provided partial refugia for petrels, even if the islands are within stoat swimming range, allowing petrels to persist for multiple generations. In contrast, petrels were apparently rapidly extirpated from islands over 100 ha, where stoats maintained a resident population.
Understanding the behaviour of invasive predators is an important step in developing effective predator control techniques. Stoats (Mustela erminea), introduced to New Zealand in the 1880s, are major predators of indigenous birds in forest, wetland, and coastal habitats, and are an emerging threat to alpine biodiversity. Stoats have recently been found to prey upon rock wrens (Xenicus gilviventris), New Zealand’s only truly alpine bird species. We monitored 32 rock wren nests using motion activated infrared (IR) cameras from 2 locations in the Southern Alps over 3 breeding seasons, 2012-2015. The behaviour of stoats that preyed upon 13 rock wren nests was quantified to describe how they behaved around rock wren nests, and to determine whether understanding these behaviours could lead to improved predator control to help to protect this vulnerable bird species. Stoats usually hunted alone. They could reach nests on cliffs and on the ground equally easily by climbing or jumping to them. Rock wren nests were attacked most frequently during the day (85% of nests) and at the chick stage in their life cycle, making this their most vulnerable stage. We suggest that this is because stoats are attracted to nests by the auditory cues of chicks calling out for food. Nests were rarely visited by stoats before or after the observed predation events. Stoats left little evidence of nest predation events beyond enlarging nest entrances. There was no indication that IR cameras or the actions of field workers affected predation behaviour, although some stoats clearly knew the cameras were there. There is an urgent need to deploy effective stoat control to recover rock wren populations. Control should focus on cliff habitats as well as on more accessible ground nests, and, if resources are limited, should primarily focus on the nestling stage. Future research could trial auditory lures to attract stoats to traps, and determine the vulnerability of rock wrens to predation outside the breeding season.
Kākāpō (Strigops habroptilus) are the only parrot species known to have a lek-based mating system. In competing for mating opportunities with females, males can fight intensely with one another, sometimes with fatal consequences. Males may have evolved more deeply hooked bills and raptorial claws than females if these confer advantage in conflicts with other males. We studied bill and claw shape in 28 museum specimens using geometric morphometrics and found no sex differences. While no claw shape sex differences were identified, we did find kākāpō lateral claws are significantly more hooked than their medial toe claws which are flatter. Claw shape in other parrot species has not yet been analysed via geometric morphometric methods, it is therefore unknown whether this claw-shape configuration is unique to kākāpō.
As ecosystem engineers, petrels are integral to ecological restoration schemes seeking to restore land sea nutrient pathways. Yet the current ranges of many petrel species are vastly reduced due to marine and terrestrial threats. Chick translocation is a demonstrated management tool for establishing seabird populations but is dependent on detailed knowledge of species breeding biology. We studied the breeding biology of white-faced storm petrel (Pelagadroma marina maoriana) on Burgess Island, Hauraki Gulf, northern New Zealand, and undertook an onsite chick translocation to investigate the efficacy of current petrel translocation practices for this relatively small species. During our study, breeding extended from August 2011 to February 2012 with hatching occurring on 6 December ± 1.2 days, a chick rearing period of 68.1 ± 0.9 days and fledging on 12 February ± 1.2 days. There was no desertion period by provisioning adults and burrow emergence began 2–6 nights before fledging. Chick growth was typical of Procellariiformes with chick mass (mean = 66.2 ± 1.7 g) peaking at 12.2 ± 1.7 days before fledging. There was no age-related change in the nightly probability of provisioning (0.54) or meal mass (mean = 7.8 ± 0.3 g). Translocated chicks fed a sardine puree diet for 11–20 days before fledging had significantly lighter fledging weights than a control group of adult provisioned chicks, but did not differ in wing length or the duration of burrow emergence before fledging. Our data suggest that translocations of white-faced storm petrel using supplementary feeding of chicks may be possible using slightly modified current feeding practices and could provide an option for expanding populations of endangered storm petrels.
Seabird bycatch data collected between 1996 and 2016 in commercial fisheries within the New Zealand Exclusive Economic Zone (EEZ) were analysed to determine if male and female grey petrels (Procellaria cinerea) have different at-sea foraging distributions during the breeding season. Data collection includes the return of bycaught (killed) seabirds from commercial fishing vessels by government fisheries observers. A total of 408 bycaught breeding grey petrels with known sex (214 males, 194 females) were analysed for a locational and seasonal sex bias. Data were also examined to determine whether where carcasses were returned from sea, there were different proportions of males and females captured by different fishing methods: offshore bottom longlining, surface longlining, and offshore trawling. There was no significant difference in the totals of male and female grey petrels returned from fishing operations, but capture locations for the sexes varied widely. More males than females were caught in April, May, August, and September. July showed a reverse trend, while June was the only month with no difference in captures between sexes. More males than females were caught in offshore bottom longliners and trawlers, with the opposite for surface longliners. This study emphasises the importance of a large-scale approach to capture locations and season when analysing impacts of fisheries on seabird populations, and highlights different foraging areas according to sex during the breeding season. Spatial segregation has important management implications as changes in fisheries practice in foraging areas may affect the sex ratio of the grey petrel population.