We found widespread nesting on the ground in a large population of feral rock pigeons (Columba livia) in an urban, but predator-free native forest reserve in Christchurch, New Zealand. Ninety-seven percent (n = 77) of rock pigeon nests were located on the ground, with most placed either at the bases of large kahikatea (Dacrycarpus dacrydioides) trees or under a tangle of vines on the forest floor.
Clutch size was 2 eggs in all nests, with a hatching success of 93.9% in nests that survived to the hatch stage. Overall nest success was higher (60.0%) than in other populations of rock pigeons, with half of nest failures attributed to culling of the population that occurred during the course of our study. On average, rock pigeons fledged 1.60 chicks per successful nest. No ground nests were located outside the boundary of the predator- proof fence, suggesting pigeons were able to assess predation risk when selecting nest site location. Ground nesting by rock pigeons may be a way to avoid damage to nests in the canopy by strong winds or predation from aerial predators such as harrier (Circus approximans), which also occur in the reserve. Based on density of nests, we estimated a breeding population of 226 to 258 rock pigeons in the 7.8 ha reserve. The high number of pigeons in the reserve highlights the need for further studies on how populations of introduced species of birds in New Zealand respond to control of mammalian predators and the effect this may have on sympatric native species.
Birds were banded in gardens at Rangiora 1961–1977, Christchurch 1977–2000, and Kaikōura 2000–2016. In total, 21,565 birds of 14 species were captured in mist-nets or traps and banded; 3,213 individuals were recovered or recaptured. The most common species banded was silvereye (Zosterops lateralis lateralis) with 15,349, followed by house sparrow (Passer domesticus domesticus) with 4,497, and common starling (Sturnus vulgaris vulgaris) with 430; all other species were less than 300 birds banded which is less than five birds per year. Distance recoveries of note are: silvereyes – Kaikōura to Wellington (153.0 km), Rangiora to Greymouth (146.0 km), Rangiora to Otira (99.0 km), with two more birds over 25.0 km; house sparrow – Christchurch to Homebush (43.5 km), with two more over 25.0 km; common starling – Rangiora to Christchurch (27.8 km); dunnock (Prunella modularis) – local movement (5.1 km). The most significant recoveries from time of banding to recovery are: silvereye – 8.8 years; house sparrow – 8.7 years; starling – 8.0 years; dunnock – 5.3 years. Wing length and mass measurements of Kaikōura birds were generally within published ranges.
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.
Thirty breeding colonies of three petrel species were found on 23 of 41 islands and one of three headlands surveyed between Milford Sound/Piopiotahi and Dagg Sound/Te Rā in Fiordland National Park, New Zealand, in November 2020. Sooty shearwater (Ardenna grisea) was the most widespread and abundant species, with an estimated 7,300 burrows on 20 islands and one mainland site. Broad-billed prions (Pachyptila vittata) were found breeding on five islands (600 burrows estimated), including an islet in Poison Bay, 70 km north-east of their previous northernmost Fiordland breeding location. We record the first evidence of mottled petrels (Pterodroma inexpectata) breeding in Doubtful Sound/Patea (on Seymour Island), which is now their northernmost breeding location. When combined with data from surveys in southern Fiordland between 2016 and 2021, more than 66,000 pairs of petrels are estimated to be present in 168 colonies in Fiordland. This total comprises 42,100–52,400 sooty shearwater pairs, 11,700–14,500 broad-billed prion pairs, 5,090–6,300 mottled petrel pairs, and at least 1,000 common diving petrel (Pelecanoides urinatrix) burrows. This is the first near-complete estimate of petrel population sizes for the Fiordland region.
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.
The Auckland Islands comprise the largest and most researched island group in the New Zealand subantarctic region, and have the largest number of endemic bird taxa. Paradoxically, they are the only one of the five island groups that has not yet been the subject of a comprehensive avifaunal review. We summarise the history of ornithological exploration of the group, and where this information is held, based on a database of 23,028 bird records made between 1807 and 2019. More than 76% of these observations were unpublished, with the two largest sources of information being Heritage Expedition wildlife logs (5,961 records) and records collected during the Second World War coastwatching ‘Cape Expedition’ (4,889 records). The earliest records of endemic taxa are summarised, along with the earliest records of significant seabird breeding colonies. Citizen science (principally eBird, with 1,597 unique records) is a rapidly growing source of information, and new records of vagrant species continue to accumulate at a rapid rate. Compared with other subantarctic islands, Auckland Islands’ birds have received very little research attention, with most effort to date focused on a few large surface-nesting seabird species.
Disequilibrium of bird communities, due to introduced pests and human-caused habitat changes, is a fundamental property to be understood in restoration of island biota. In this paper, we suggest that the reestablishment of native forests and food webs favour long-established and native species, and is less favourable to more recently introduced species. To test this hypothesis, we compared population trends of native and non-native birds on five islands in the Ipipiri Group in the north of New Zealand. We used over 900 station counts starting in 2008 when habitat recovery and pest (rat [Rattus], mouse [Mus musculus], and stoat [Mustela erminea]) removal began, as well as comparing to a set of earlier counts. In general, we found that detection rates of most long-established endemic native species significantly increased, while non-native species mostly decreased, suggesting population increases and decreases, respectively. Of the native species, six are relatively recent natural immigrants to New Zealand, and most of these declined or remained unchanged. We suggest that the increase in long-established natives is likely due to increased size and quality of native bush areas making habitat more favourable to these natives, as well as reduced predation and competition from the pest mammals.
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.
The white-capped mollymawk (Thalassarche cauta steadi) and Tasmanian mollymawk (T. cauta cauta) have discreet breeding sites, but away from their breeding grounds, where their at-sea ranges overlap, they are difficult to identify. The bill colour of these taxa has recently been considered to differ, but there is much conflicting information in published accounts. Three key differences often discussed are the amount of yellow on the culminicorn, the amount of yellow on the cutting edge to the upper mandible, and the amount of darkness on the mandibular unguis. In January 2018 I assessed these characters in 100 adult white-capped mollymawks at their Disappointment Island breeding site and found that each character was variably present. The majority of white-capped mollymawks lacked a yellow base to their culminicorn and had a dark mark on their mandibular unguis. In contrast, it has been reported that the majority of adult Tasmanian mollymawks have yellow at the base of their culminicorn and lack a dark mark on their mandibular unguis. While these characters can be used as a guide to identify these taxa, a minority of individuals of each taxon show the ‘typical’ bill colours of the other taxon. The amount of yellow on the cutting edge to the upper mandible varied between individual white-capped mollymawks, and so this is not a useful identification character.
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.