# Hutton's shearwater

Hutton's shearwater (Puffinus huttoni; also known in Māori as kaikōura tītī) is a medium-sized ocean-going seabird in the family Procellariidae. Its range is Australian and New Zealand waters, but it breeds only in mainland New Zealand. Its conservation status is Endangered, because there are just two remaining breeding colonies, located in the Seaward Kaikōura Range. Six other shearwater colonies have been wiped out by introduced pigs. Hutton's shearwater is the only seabird in the world that is known to breed in alpine areas. Conservation measures for the bird include community initiatives to rescue birds that crash-land at night on streets in Kaikōura, and the establishment of a protected area on the Kaikōura Peninsula including a predator-proof fence, man-made burrows, and translocating fledglings from the remaining colonies.

## Description

The bird's name commemorates Frederick Hutton, a former curator of the Canterbury Museum in Christchurch, New Zealand. A medium-sized (350 g) seabird, with a 75 cm wingspan, it is brown with a white underbelly and brown collar, dark borders to the underwing, dark grey bill, and pinkish dark-webbed feet; it can be distinguished from fluttering shearwater by its dark grey "armpits". At a breeding colony it has a loud cackling call.

## Ecology

Hutton's shearwater feeds in the open ocean largely on small fish and krill, diving up to 20 m. Puffinus huttoni have long bills, which are adapted to catch prey more or less underwater by plunging from a few metres above the surface or by paddling slowly forwards searching with their head submerged, then diving using partly opened wings for propulsion.

## Distribution

These birds live entirely at sea except when breeding. During the September–March (spring and summer) breeding season, adults migrate to New Zealand waters; there have been individual sightings around the entire New Zealand coast, but most birds are feeding off the eastern South Island, especially between Cook Strait and Banks Peninsula. Large flocks can be seen off the Kaikōura coast during summer. Outside the breeding season, they are mostly found in Australian waters. Geo-locators fitted on young birds revealed some circumnavigate Australia in an anti-clockwise direction in the 4–5 years leading up to sexual maturity.

## Breeding

Uniquely amongst seabirds, Hutton's shearwater breed in the sub-alpine to alpine zones, making them one of the few New Zealand seabirds to breed solely on the mainland. Their burrows are at an altitude of 1200–1800 m. They formerly bred in both the Seaward and Inland Kaikōura mountains in historic times, and Māori collected the young "muttonbirds" before they could fly for food. Comparing extant and extinct colonies, the key difference is the presence of introduced wild boar. The birds are absent from New Zealand waters outside of the breeding season and adult birds start returning from Australia in late August. Their breeding is restricted to only two remaining colonies in the Seaward Kaikōura Range, one of over 100,000 pairs at the head of the Kowhai River, and one small (8000 pair) colony on private land at Shearwater Stream. Intraspecific competition has been observed between male conspecifics as they will defend their burrow from others. Although the species was scientifically described in 1912, its breeding colonies were only rediscovered by Geoff Harrow in 1964. Burrows are dug into steep tussock slopes at a density of 1 per 2 m$^2$. Hutton's shearwaters burrows are simple and non-branching. Kowhai Valley colony burrows are dug on slopes varying from moderate to steep because the soil here is deeper and friable, shallower slopes are less suitable for burrows.
Most reliable method of measuring breeding success and burrow occupancy is with inspection hatches, even though it causes a disturbance, they can tolerate it well. Over 70% of burrows were occupied by an incubating bird during the early stages of the breeding period. Most breeding pairs will lay one white egg in November which is incubated for 50 days and the responsibility is shared by both sexes; chicks will be fledged in around 80 days. Egg laying within a colony is non-synchronous. Mid November is the early incubation stage while late incubation occurs in early January, chick rearing is also from early January and ends in late February. Seasonal variation affects the rate of mass gained by chicks during the fledging period. Annual adult survival has been estimated to be 93.1% with breeding success averaging 46.5% but Puffinus species breeding in introduced predator-free environments have comparable breeding success and adult survival rates. Breeding success in the Kowhai Valley and Shearwater Stream colonies during the 2006/07 and 2007/08 breeding season were lower than in the late 1990s even though burrowing occupancy rates were similar. Shearwater Stream breeding success was significantly lower than Kowhai Valley for both of these breeding seasons despite efforts to control stoat population, indicating that predation is not the primary cause of breeding failure. In the case of breeding failure and the egg is unsuccessful, a replacement egg will not be laid.

## Feeding
### Foraging Strategy

Many shearwater species feeding strategy is an intermediate between pursuit diving and surface feeding. Hutton's shearwater foraging strategy is exclusively pursuit diving as they dive for prey. On average, birds will dive a depth of 5.6m but can dive as deep as 35m. Birds that are incubating will dive deeper than birds that are feeding chicks. When at-sea feeding conditions are poorer, breeding success is lower so there is selective pressure on adult birds to forage adequately. Individuals have been observed foraging with red-billed gulls, black-backed gulls, white-fronted terns and Hector's dolphins but with varying diving depths and prey preference, niche differentiation may be occurring. Hutton's shearwater will dive nearly always during the day, indicating that vision is a large part of their foraging strategy, with rare night-time dives happening within 72 hours of a full moon. Dives occur as early as 5am all the way up to 10pm, while rafting occurs after 10pm until 5 am. Rafting helps to conserve energy when they cannot forage without light. Minimal movement during rafting confirms the birds are not foraging at all, supported by the fact that birds do not raft in the same area as foraging and go to areas with deeper waters than their foraging locations. Diving depth and frequency both vary with time of day and breeding stages with dives being more frequent around dawn and dusk, consistent with the diurnal vertical migration of prey species, but dive frequency between 6pm and 8pm during the chick rearing period is significantly reduced. Less frequent dives at dusk for other seabirds could be to reduce energy expenditure during foraging by allowing potential prey to return to the surface or because birds are returning closer to their colony before foraging as more energy is required to carry resources from a greater distance.

### Diet and Foraging Locations

Hutton's shearwater feed on what is available within 50m of the surface and can range from small fish, crustaceans, krill and cephalopods. Using GPS trackers on adult birds from the Kaikōura Peninsula colony, 4 main foraging locations have been identified with 2 being coastal (Pegasus Bay and Canterbury Bight) and 2 over oceanic banks (Mernoo Bank and Urry Bank). All the foraging locations were approximately 125-365km south or south-east of the colony and near Banks Peninsula. Average trip duration and distance is 5 days and 1092.9km with the total ranging from 1-15 days and 264-2157km. Foraging locations all share the same trait as areas with high chlorophyll-a and waters shallower than non-foraging locations. Using stable isotopic analysis of induced feathers and different prey collection samples from the foraging sites, it was estimated that Hutton's shearwater predominantly feed on small fish, crustacean larvae and cephalopods, with prey diversity being greatest in November. Increased prey diversity correlates with the egg-laying and incubating stage, the birds are less specific on what they eat at this time so long as they can get food quickly and return to their burrow. Isotope analysis for the composition of induced feathers is more similar to the prey samples collected near Banks Peninsula than samples collected near Kaikōura which suggests the birds are flying and foraging in areas further away from their colony. Few birds may spend the early morning in close proximity to Kaikōura before travelling away, during their near-shore movements no dives were recorded however, supporting the idea that Hutton's shearwater do not forage near their colonies.

## Conservation
### Threats to the breeding colonies

The eight breeding colonies discovered in 1964 have been reduced to two, known now as the Kowhai Valley and Shearwater Stream Important Bird Area; the other lower-altitude colonies were destroyed by feral introduced pigs. The breeding birds' main predators are introduced stoats, which kill about 0.25% of adults and 12% of chicks each year in their nesting burrows. The overall growth rate is still positive, though, so stoats are not considered a major threat.
Some parts of the colonies are in steep, unstable sites. The browsing of deer, goats, and pigs in these steep areas has contributed to erosion, which has damaged the Hutton's shearwater burrows and the population. However, control of pigs has led to better vegetation cover at the colonies and lessened destruction of burrows.
The 2016 Kaikōura earthquake caused landslides in the largest remaining breeding colony at Kowhai Valley, and occurred during the breeding season. Initial reports indicated a loss of half of the colony. Subsequent work in 2017 indicated the loss was 20-30% of breeding burrows, but that there was a lot of bird activity observed in the nesting areas.
As at 2017, the estimated population size is 600,000 individuals, including 150,000 breeding pairs. Current estimates suggest that earlier studies significantly under-reported the population. However, both of the remaining breeding colonies are vulnerable to predators or erosion.

### Artificial colony

As a further conservation measure, in 2005 a new colony (Te Rae o Atiu) was established on the Kaikōura Peninsula. First, a small transfer of 10 nestlings was sent in April 2005. After that, roughly 100 additional nestlings were moved annually each March in 2006, 2007, 2008, 2012 and 2013. Chicks translocated from the Kowhai colony were hand-fed in artificial burrows to ensure they would imprint on the new colony, and since 2010 have been returning there to breed. A predator-proof fence was built around the 2 hectares (4.9 acres) site in February 2010 by the Hutton's Shearwater Charitable Trust.

### Crash-landing (fallout)

Hutton's shearwaters are nocturnal, and can be disoriented by bright lights at night. This has led to problems with adult and newly-fledged birds crash-landing in the streets of Kaikōura at night. During the season when the fledgling birds leave their mountain burrows, volunteers in Kaikōura patrol the streets, looking for birds that have crash-landed on roads in the town. The young birds are usually unable to take off again, making them vulnerable to being run over by vehicles or succumbing to predation by dogs or cats. In 2015, over two successive nights, there were 200 birds found crash-landed in the town. A new facility, the Hutton's Hub, was opened in 2016 adjacent to the Department of Conservation office, as a place for the community to bring in crash-landed birds. Any birds that can be rescued are taken to a rehabilitation centre for later release at sea. The community volunteer programme results in around 80% of the crash-landed birds being successfully released.

### Dark Sky Sanctuary

A new initiative was launched in 2022 to seek accreditation of a dark-sky preserve in the Kaikōura area. This could reduce the problems that lighting causes for Hutton's shearwaters. The Kaikōura District Council had already modified streetlighting, to reduce the risk to the birds. In April 2022, the Mayor of Kaikōura said that the dark sky reserve initiative had the full support of the council, and would be a boost to tourist numbers, especially during the winter period. The Kaikōura Dark Sky Trust applied to DarkSky International for designation as an International Dark Sky Sanctuary in August 2024. The designation was announced on 11 September 2024. The sanctuary covers an area of 2,039 km$^2$ (787 sq mi), representing around 98% of the Kaikōura District, excluding the Kaikōura township. The Trust plans to apply for the Kaikōura township to be recognised with international dark sky community status.

## Gallery

* Puffinus huttoni
* Hutton's Research Hut - Kowhai Colony
* Partly grown chick at Te Rae o Atiu
* Fully grown chick at Te Rae o Atiu
* Hutton's at sea