To investigate factors that might influence calling rates of morepork (ruru, Ninox n. novaeseelandiae), Song Meter SM2+ acoustic recorders were deployed for 12 months recording every night at Hodges Bush (a remnant forest) and Trounson Kauri Park (TKP) in Northland, New Zealand. Three call types were recorded: the classic ‘morepork’ hoot, the ‘wheel’ and ‘wok’. There was no strong seasonal variation in ‘morepork’ hoots from Hodges Bush, although there were fewer hoots from February to March. At TKP, the number of hoots declined from June to August, but the number of ‘wheel’ and ‘wok’ calls remained constant. At dusk, ‘Morepork’ hoots gradually increased until they were at their greatest frequency 3 hours after sunset at both sites. Thereafter, the number of calls reduced through the night at TKP, but remain constant at Hodges Bush until a second peak 2 hours before dawn, after which numbers drop off markedly. The other two call types were constant throughout the night at both localities, but with a pre-dawn peak at Hodges Bush. There was no significant correlation between calls and moon phase at either site. We suggest that it is possible to use vocal activity as a means of monitoring morepork population changes, but more studies are needed to determine variations between sites and different population densities.
We describe the creation of a standardised set of data from the two national atlases of bird distribution compiled by the Ornithological Society of New Zealand. The data provide estimates of local occupancy probability for each of 64 taxa of native land birds, in each of 2,155 grid squares covering the North, South, and Stewart islands, in two measurement periods (September 1969 – December 1979, and December 1999 – November 2004). Because these local occupancy estimates were derived on an identical basis for each bird taxon and each time period, they enable unbiased comparisons between time periods and among species. Links to permanent data repositories of the original and standardised data are provided.
We use previously published and new data from a long-term study of the red-billed gull (Larus novaehollandiae scopulinus) population at the Kaikoura Peninsula to review causes and consequences of population change. Currently the largest colony in New Zealand, the Kaikoura population, has undergone major changes over the past 52 years. In 1994 the population began to decline, and between 1983 and 2003 it dropped by 51%. Fledging success varied markedly between seasons. The major cause of reproductive failure was predation by introduced mammals, especially ferrets (Mustela furo) and feral cats (Felis catus). These predators became a problem when rabbits (Oryctolagus cuniculus) and hares (Lepus europaeus) increased in number, enhancing the predators’ survival over-winter. Periodic failure in the availability of euphausiids, the main food of red-billed gulls, swamping of nests during high seas, and chilling of nestlings during long periods of bad weather also have been set backs to the population. However, in the absence of predation, these factors produced only a temporary impact to the population of long-lived gulls. The decline in both body size and survivorship of adults over the last 5 decades indicates that there are other factors at work, and indicate that the population has experienced some form of unfavorable environmental condition or stress over a long period.
Acrocephalus warblers occur across Eurasia, Africa, and Australasia, where they are typically migratory, wetland species, but also occur on islands as sedentary endemics in drier habitats, including forest and scrub. External morphology and song amongst Pacific island Acrocephalus warblers were investigated and comparisons made with Acrocephalus species elsewhere. There was a range of sizes between Pacific island Acrocephalus warblers, many being larger than migratory continental species. Bill:wing length ratios were higher in most Pacific species, and their wings more rounded, than most continental species, but less rounded than swamp-warblers of Africa and adjacent islands. Plumages of W and N Pacific species resembled reed-warblers elsewhere, but in SE Polynesia were more varied, brown or grey dorsally, shaded olive, yellow or rufous, and pale ventrally, shaded white, yellow or buff-white, with a melanistic morph on Tahiti. Spectrographic analysis showed a gradient of song complexity from continental and Marianas/Micronesia species (A. hiwae, A. syrinx), through to A. taiti and A. vaughani on the Pitcairn islands, which had no song. The mean frequency of Pacific island reed-warbler songs was inversely correlated with mean body size.
A national survey of breeding red-billed gulls (Larus novaehollandiae scopulinus) was carried out during 2014–2016 to establish the present status of the species. Observers were asked to find and report all breeding colonies, starting with a check of previously reported breeding sites. Standardised means of conducting these surveys were developed, publicised, and largely applied. Around 27,831 pairs of red-billed gulls were recorded nesting in New Zealand during the survey: 14,713 pairs at 122 South Island sites; 12,676 pairs at 124 North Island sites; and 442 pairs at 14 sites on the Chatham Islands. Other than colonies on the Three Kings Islands (1,763 pairs) and Takapourewa/Stephens Island (1,250 pairs) there were no large concentrations on offshore islands. The largest mainland concentrations were at Kaikoura (3,210 pairs), Taiaroa Head (2,145), Rotorua (2,277) and Marsden Point (1,190). Although the accuracy of previous estimates is questionable, the red-billed gull nevertheless appears to have declined nationally since the mid-1960s. Possible reasons for the decline are discussed and a proposal for future monitoring of the species is proposed.
In September 2002 and 2014 respectively, 2,077 and 1,704 prospecting Hutton’s shearwaters were colourmarked on the ventral plumage at their breeding grounds at Kōwhai River, Seaward Kaikōura Ranges, New Zealand. Large numbers (425,516 in 2002, and 106,900 in 2014) of marked and unmarked birds were then counted from small boats off the Kaikōura coast between Haumuri Bluff and Ohau Point. A hypergeometric sampling model was fitted these counts, leading to population estimates of N =̂ 459,290 (95% CI = 434,306-484,733) birds in 2002 and N ̂ = 590,407 (95% CI = 543,992–642,697) individuals in 2014. These estimates include both breeding and non-breeding birds and indicate that between 2002 and 2014 the population trend was about +2% per year.
Weights and body measurements from 258 male and 203 female adult (>1 year) and juvenile (
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.