A published national survey of red-billed gulls (Larus novaehollandiae scopulinus) in 2015 recorded about 28,000 nests in New Zealand, a 30% decrease in 50 years. We compared nest numbers in 2020 at Otago, south-eastern South Island, with published records for 1992–2011 and 2015. In contrast to trends further north, numbers at Otago have increased but the average annual rate of increase dropped from 6–10% for 1992–2011 to 2% for 2011–2020. Citizen science provided a valuable input in 2020 with records of breeding at previously undocumented urban locations. The about 6,000 nests at Otago in 2020 probably account for 20% of the national total.
The description of the long-tailed cuckoo’s (Eudynamys taitensis) egg was uncertain until the 1930s. Edgar Stead published evidence in 1936 that it was white with darker (red-brown or purplish) speckles, and therefore mimetic in colour and pattern (as well as size) to the eggs of many small song-birds in New Zealand. In reviewing eggs in museum collections, I find that only one (Auckland Museum LB8968) is certainly long-tailed cuckoo, and only eight other eggs are “probable” (with another eight “possible”). Average dimensions of the nine most likely eggs are 24.1 x 17.4 mm. Field observations of long-tailed cuckoo nestlings, or dependent fledglings receiving food, mostly involve whiteheads, yellowheads, and brown creepers (all in the genus Mohoua, Mohouidae), the principal biological hosts. There are single credible reports of a long-tailed cuckoo nestling being raised in a nest of South Island robin (Petroica; 1880s), silvereye (Zosterops; 1946, plus a vague record from the 1980s), and fantail (Rhipidura; 1963). The scarcity of evidence for non-mohouid hosts, despite the great increase in ornithological field-work since 1963, suggests that use of secondary hosts is extremely rare. Seven other New Zealand song-birds have been cited as hosts of the long-tailed cuckoo, but all reports lack evidence of a cuckoo nestling being raised by the species concerned.
Conservation management requires knowledge of the distribution of species and how this changes over time. Great spotted kiwi (roroa, Apteryx maxima) is classified as globally threatened, ‘Vulnerable’ by the IUCN. It occurs only in the northwest of the South Island of New Zealand, is nocturnal and occurs at low density in mainly remote, mountainous terrain. To determine its distribution, we deployed acoustic recorders at 1,215 locations across 1,400,000 ha between 2012 and 2021. We analysed 3,356 nights of recordings to determine presence and call rates at each location. Roroa were distributed across 848,000 ha, but we identified a core area in northwest Nelson representing just 12% of the distribution (101,000 ha). Within the core, call rates exceeded 3 calls/h at many locations. Call rates provide only a relative indication of abundance but, outside the core, call rates fewer than 0.3 calls/h are common, suggesting that roroa are relatively sparse over much of their distribution. We used a static occupancy model with climatic, topographic and land-cover class variables to better understand the distribution. Eighty percent of recorder-nights had a detection probability exceeding 50%. At this probability, 73% of 5 x 5 km cells surveyed were sampled sufficiently to exceed 90% probability of detection if roroa were present. Annual rainfall and land-cover class appear most important for modelling occupancy. However, comparison of probability of occupancy and actual distribution suggests that variables not included in the modelling, which might include predation, also affect the distribution.
This study assessed how tall mangroves were used by a pair of banded rails (Gallirallus philippensis assimilis) with dependent young during three breeding seasons and the intervening periods. Banded rails were territorial and resident all year, raised their young under the mangrove canopy predominantly in dense pneumatophores, and sub-canopy seedlings and saplings. Foraging rails did not follow the tide as it covered and uncovered the flats. Young less than 20 days old were left in cover and delivered food. Young then followed parents as they strolled throughout the site, swam, flew short distances, and climbed mangroves. Rails bathed in and drank saline water and ate worms and crabs. The dependence period of broods was 45–49 days, and in one season, a young bird stayed within the natal site until it was 59 days old.
A high resolution chronology of deep water charophyte algal remains in the Pyramid Valley lake deposit, North Canterbury, South Island, New Zealand, records the presence and drainage of a previously unsuspected much larger (c. 50 ha) lake. The larger lake occupied the surrounding basin and the present lake (1 ha) was a semi-isolated embayment at its south-western margin. Fluctuating lake levels and its final drainage drove changes in the vegetation and hence in the habitats available for the avifauna recorded in the rich fossil record. A high precision radiocarbon age on the only South Island goose (Cnemiornis calcitrans) in the fauna coincided with the presence of lowland forest and not with the brief period when sedges and grassland colonised the newly exposed former lake bed. This suggests that the South Island goose was able to survive in different habitats through successive glacial-interglacial vegetation cycles. Information from other disciplines can be essential to interpreting both a fossil site and the circumstances surrounding the presence of a particular species in it.
New Zealand falcons (Falco novaeseelandiae) routinely feed on burrow-nesting seabirds (petrels: Procellariiformes) at several sites. As petrels are rarely present on the colony surface during daylight, and falcons are considered to be diurnal hunters, there has been much speculation about how falcons are able to capture petrels. We present evidence that New Zealand falcons are able to hunt petrels in forest at night, and also enter burrows during the day to extract chicks. These are novel hunting behaviours for falcons, and further increase the broad range of hunting strategies documented for New Zealand falcons. While these hunting methods may be used by only a few individual birds, they can produce high prey-capture rates.
Artificial mallard (Anas platyrhynchos) nests were used to identify potential nest predators and assess whether small, farm-scale predator control could reduce mallard nest predation in Southland, New Zealand. Artificial nests were deployed over the mallard nesting period (late winter – spring) in both 2019 and 2020 and monitored with motion detection cameras. Prior to 2020 artificial nest deployment, farm-scale trapping of mammalian predators was conducted on one farm whilst the other was left as a control. Feral cats (Felis catus), brushtail possums (Trichosurus vulpecula), and European hedgehogs (Erinaceus europaeus) frequently visited the artificial nests but seldom preyed on them (i.e. consumed the eggs). Swamp harrier (Circus approximans) were the most common predator and were responsible for the destruction or predation of at least one egg at 17% of the artificial nests. Mammalian predator trapping had no noticeable effect on artificial nest predation, but did reduce the probability an artificial nest was visited by a cat, possum, or hedgehog. Results suggest typical predator control efforts of gamebird hunters does not reduce mallard nest predation, but may reduce nest disturbance and consequently mallard hen predation and nest abandonment.