The black-billed gull (''Chroicocephalus bulleri''), also called Buller's gull or (

Māori Māori or Maori can refer to: Relating to the Māori people * Māori people of New Zealand, or members of that group * Māori language, the language of the Māori people of New Zealand * Māori culture * Cook Islanders, the Māori people of the Co ...

), is a

Near Threatened A near-threatened species is a species which has been Conservation status, categorized as "Near Threatened" (NT) by the International Union for Conservation of Nature (IUCN) as that may be vulnerable to Endangered species, endangerment in the ne ...

species of

gull Gulls, or colloquially seagulls, are seabirds of the subfamily Larinae. They are most closely related to terns and skimmers, distantly related to auks, and even more distantly related to waders. Until the 21st century, most gulls were placed ...

in the family

Laridae Laridae is a family of seabirds in the order Charadriiformes that includes the gulls, terns (including white terns), noddies, and skimmers. It includes around 100 species arranged into 22 genera. They are an adaptable group of mostly aerial bird ...

. This gull is found only in

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

, its ancestors having arrived from

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

around 250,000 years ago.

Taxonomy

Originally named ''Gavia pomare'' in 1855 by

Carl Friedrich Bruch Carl Friedrich Bruch (March 11, 1789 – December 21, 1857) was a German ornithologist. He was the younger brother of bryologist Philipp Bruch (1781–1847).Sir Walter Lawry Buller because it was already being used for another species. He then took up

Prince Napoléon Bonaparte A prince is a male ruler (ranked below a king, grand prince, and grand duke) or a male member of a monarch's or former monarch's family. ''Prince'' is also a title of nobility (often highest), often hereditary, in some European states. The fe ...

's "playful" genus name ''Bruchigavia'' (literally, "Bruch's seabird") as a provisional name for New Zealand gulls. But because Buller's proposed species name ''melanoryncha'' (literally, "black-billed") had already been given to another gull species, Frederick Hutton suggested the name ''bulleri'', in honor of Buller, in 1871. Buller accepted the offer and followed others in adopting the "larger and better-defined genus" of ''

Larus ''Larus'' is a large genus of gulls with worldwide distribution (by far the greatest species diversity is in the Northern Hemisphere). Many of its species are abundant and well-known birds in their ranges. Until about 2005–2007, most gulls ...

''. The alternative common name Buller's gull also retains the connection to Buller. The species is now considered to belong within the genus ''

Chroicocephalus ''Chroicocephalus'' is a genus of medium to relatively small gulls which were included in the genus ''Larus'' until genetic evidence published in 2005 showed that ''Larus'' as then constituted was paraphyly, paraphyletic. Ten species are currentl ...

''. The

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

is in the collection of the

Museum of New Zealand Te Papa Tongarewa The Museum of New Zealand Te Papa Tongarewa is New Zealand's national museum and is located in Wellington. Usually known as Te Papa ( Māori for ' the treasure box'), it opened in 1998 after the merging of the National Museum of New Zealand ...

Description

A healthy adult black-billed gull is typically 35–38 cm long, with a wingspan of 81–96 cm, and a weight of around 230g. The head, body, and parts of the wings are white, with silvery grey on the saddle and wings, as well as black edging on the wings. The gull also undergoes some seasonal color change. While typically black from February to June, the

orbital ring An orbital ring is a concept of an artificial ring placed around a body and set rotating at such a rate that the apparent centrifugal force is large enough to counteract the force of gravity. For the Earth, the required speed is on the order of ...

is orange-red, red, or dark red the rest of the year. The legs, too, change from black to dark red and even bright red as the breeding season progresses, "possibly stimulated by presence of begging chicks and juveniles." Observations suggest the gull is sexually dimorphic, but there is a lack of published data to support this. There is likewise a lack of data in regard to geographical variation. Easily mistaken for the red-billed gull, the black-billed gull is distinguished by its black bill and is described as having a "more delicate appearance", a "more buoyant and graceful" flight, and being "generally less noisy", despite having a similar call. F1 and F2 hybrids between the two gulls have been observed, both hybrids exhibiting dark red bills.

Behaviour

Colonies are formed around the first pair that begins nesting. Where more than one pair forms the initial nest, clustering around these sites takes place within the colony. Colonies are frequently tightly packed, with "Gulls little more than pecking distance from each other and nests often touch, leaving little room for taking off and landing". Males may display aggressive behaviour towards others in an "ill-defined area" for a few minutes before leaving the area and forgetting it. Nonetheless, not all male aggression is linked to defending a particular area, and some pairs without chicks will show aggression towards those with chicks. Fights are rarely prolonged, usually consisting of a single attack by the aggressor, employing the bill for pecking, the wings for beating, and the legs for scratching. The target typically retreats right away. Adults roost at the breeding colony or feeding sites, though the latter is more common. Black-billed gulls can find themselves in conflict with humans. In 2024, black-billed gulls nesting in the "

Christchurch Seagull Pit The Seagull Pit is a derelict building site and tourist attraction on Armagh Street in the Christchurch Central City, New Zealand. The pit was formed when the derelict basement of the former PricewaterhouseCoopers Building became flooded by rain ...

" near

New Regent Street New Regent Street is a pedestrian mall in Christchurch. Built as a private development in the early 1930s with 40 shops in Mission Revival architecture, Spanish Mission architectural style, it is one of the city's major tourist attractions. Prov ...

were deemed a "menace" by locals. They had been nesting in the flooded foundations of a demolished office block nearby, and had spread to nesting on nearby rooftops. The gulls were causing a nuisance by stealing food from tables and fouling the area. A local café owner said, "They shit everywhere. They’re also not afraid of people any more. They’ll swoop down and get food off your plate. They dive bomb. Small children don't stand a chance." Due to their protected status, nothing could be done to remove the birds.

Distribution and habitat

The black-billed gull is

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

to New Zealand. Up to 78% of the total population is estimated to be living in the Southland region, on the southern end of the

South Island The South Island ( , 'the waters of Pounamu, Greenstone') is the largest of the three major islands of New Zealand by surface area, the others being the smaller but more populous North Island and Stewart Island. It is bordered to the north by ...

. In breeding season the gull is found on major rivers, especially

braided river A braided river (also called braided channel or braided stream) consists of a network of river channel (geography), channels separated by small, often temporary, islands called ''braid bars'' or, in British English usage, ''aits'' or ''eyots''. ...

s, lakes, and farmland. It generally prefers estuaries and coastal areas outside of the breeding season, though some can be found at breeding sites all year round. The gull is also attracted to urban areas, and "anywhere refuse of scraps available", such as rubbish dumps and

freezing works In livestock agriculture and the meat industry, a slaughterhouse, also called an abattoir (), is a facility where livestock animals are slaughtered to provide food. Slaughterhouses supply meat, which then becomes the responsibility of a meat ...

. In 2019 some gulls established a colony of around 300 birds in

Christchurch Central City Christchurch Central City or Christchurch City Centre is the geographical centre and the heart of Christchurch, New Zealand. It is defined as the area within the Four Avenues (Bealey Avenue, Fitzgerald Avenue, Moorhouse Avenue and Deans Aven ...

. The species has been sighted occasionally on

Stewart Island Stewart Island (, ' glowing skies', officially Stewart Island / Rakiura, formerly New Leinster) is New Zealand's third-largest island, located south of the South Island, across Foveaux Strait. It is a roughly triangular island with a la ...

and

The Snares The Snares Islands (; officially Snares Islands / Tini Heke), known colloquially as The Snares, is a group of uninhabited islands lying about south of New Zealand's South Island and to the south-southwest of Stewart Island / Rakiura. The Snar ...

, as well as at altitudes of up to 1700

MASL The Major Arena Soccer League (MASL) is a professional indoor soccer league in North America. The MASL features teams playing coast-to-coast in the United States and Mexico. The league is the highest level of arena soccer in North America. The le ...

on the mainland. Various colonies also live on the

North Island The North Island ( , 'the fish of Māui', historically New Ulster) is one of the two main islands of New Zealand, islands of New Zealand, separated from the larger but less populous South Island by Cook Strait. With an area of , it is the List ...

, though it was formerly only a "visitor", the first recorded breeding taking place at

Lake Rotorua Lake Rotorua () is the second largest lake in the North Island of New Zealand by surface area, and covers 79.8 km2. With a mean depth of only 10 metres it is considerably smaller than nearby Lake Tarawera in terms of volume of water. It i ...

in 1932. Some South Island birds cross the

Cook Strait Cook Strait () is a strait that separates the North Island, North and South Islands of New Zealand. The strait connects the Tasman Sea on the northwest with the South Pacific Ocean on the southeast. It is wide at its narrowest point,McLintock, ...

after breeding season to winter in the North Island.

Important Bird Areas

Sites identified by

BirdLife International BirdLife International is a global partnership of non-governmental organizations that strives to conserve birds and their habitats. BirdLife International's priorities include preventing extinction of bird species, identifying and safeguarding i ...

as being important for black-billed gull conservation are: ;

Canterbury Canterbury (, ) is a City status in the United Kingdom, city and UNESCO World Heritage Site, in the county of Kent, England; it was a county borough until 1974. It lies on the River Stour, Kent, River Stour. The city has a mild oceanic climat ...

region *

Ashburton River / Hakatere The Ashburton River / Hakatere is a river in the Canterbury region of New Zealand, flowing across Mid Canterbury from the Southern Alps to the Pacific Ocean. The official name of the river was amended to become a dual name by the Ngāi Tahu Cl ...

Ōpihi River The Ōpihi River flows through south Canterbury, in New Zealand's South Island. It has been identified as an Important Bird Area by BirdLife International because it supports breeding colonies of the endangered black-billed gull. Description T ...

Opuha Dam The Opuha Dam is located on the Opuha River, a tributary of the Ōpihi River in South Canterbury, New Zealand. The dam is used for water storage for farming irrigation and provides 7.7 MW of electricity to New Zealand's national grid. The site ...

Orari River The Orari River is a river of the south Canterbury region of New Zealand's South Island. It rises to the northwest of the Four Peaks Range, initially flowing north then east to circumnavigate the range before flowing southeast across the Canter ...

Rakaia River The Rakaia River is in the Canterbury Plains in New Zealand's South Island. The Rakaia River is one of the largest braided rivers in New Zealand. The Rakaia River has a mean flow of and a mean annual seven-day low flow of . In the 1850s, Europ ...

; Southland region *

Aparima River The Aparima River, earlier known as Jacob's River, is one of the southward-flowing braided rivers of Southland, New Zealand. Description The Aparima has its headwaters in the Takitimu Mountains, south of Lake Te Anau, and flows south for befo ...

* Eyre Creek *

Mararoa River The Mararoa River is one of the braided rivers of the Southland Region of the South Island of New Zealand. The New Zealand Ministry for Culture and Heritage gives a translation of "long-lasting cultivations" for ''Māraroa''. Description The ...

Mataura River The Mataura River is in the Southland Region of the South Island of New Zealand. It is long. Description The river's headwaters are located in the Eyre Mountains to the south of Lake Wakatipu. From there it flows southeast towards Gore, New ...

Ōreti River The Ōreti River (formerly the Oreti River) is one of the main rivers of Southland, New Zealand, and is long. The river has been identified as an Important Bird Area by BirdLife International because, for much of its length, it supports bree ...

Whitestone River The Whitestone River () is a river in New Zealand, a tributary of the Mararoa River. It has been identified as an Important Bird Area by BirdLife International because it supports breeding colonies of the endangered black-billed gull. See als ...

Status

In regard to Southland colonies, Rachel McClellan notes that "surveys in the 1970s indicated a population of about 140,000 breeding birds, whereas recent counts gave estimates of only 15–40,000 breeding birds". Nonetheless, different counting methods and the various limitations of these methods mean that "estimates must be treated with caution". This suggests a 6% decline in population every year across thirty years, equivalent to up to 83.6% over the whole period, or 50% if the data are taken conservatively. Higher population sizes in the 1950s and 1960s were potentially the result of increased agricultural activity, but the correlation is tenuous. Populations at this time were of legendary proportions, with anecdotes telling of farmers who "were forced to wear raincoats so as not to be coated in droppings". Due to "very rapid decline over three generations" the

IUCN The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the status ...

has rated the species as

. The gull had earlier received a Least Concern rating in 1994, and a Vulnerable rating in 2000. The

New Zealand Department of Conservation The Department of Conservation (DOC; Māori language, Māori: ''Te Papa Atawhai'') is the public service department of New Zealand charged with the conservation of New Zealand's natural and historical heritage. An advisory body, the New Zealand ...

listed the gull as Nationally Critical in 2016. It has been referred to in other publications as "critically endangered", and James Westrip proposed in August 2018 that the gull's status be uplisted to

Critically Endangered An IUCN Red List critically endangered (CR or sometimes CE) species is one that has been categorized by the International Union for Conservation of Nature as facing an extremely high risk of extinction in the wild. As of December 2023, of t ...

in the next BirdLife International Red List report, though it was eventually downlisted in 2020. Bill Morris calls the bird "the world's rarest gull".

Threats

In her study of Southland colonies of black-billed gulls, Rachel McClellan found that eighty per cent of observed chick deaths resulted from predation. Introduced mammals, namely ferrets, stoats, cats, and hedgehogs, constitute the "primary factor influencing productivity", that is, nest success, in the colonies. Chick predation from the indigenous black-backed gull (''Larus dominicanus'') also threatens the black-billed gull population. While "the species is relatively tolerant of human disturbance", having potentially benefitted from increasing land conversion for agricultural use since the arrival of Europeans, human activity has also had a negative impact on population size. Largescale shootings of black-billed gulls, such as a 2009 "massacre" of around 200 birds in North Canterbury, are particularly detrimental to the species' future. A similar event was reported in December 2018, while another article tells of a gull being discovered with an arrow in it. The birds have also been targeted by people in vehicles who "occasionally plough through colonies". Morris suggests such actions in part result from confusion with the more common and disliked

red-billed gull The red-billed gull (''Chroicocephalus novaehollandiae scopulinus''), also known as tarāpunga and as the mackerel gull, is a native gull, seagull of New Zealand, being found throughout the country and on outlying islands including the Chatham I ...

(''Chroicocephalus novaehollandiae scopulinus''), which is nonetheless also endangered in New Zealand. Although no studies have been conducted in this area, previous

DDT Dichlorodiphenyltrichloroethane, commonly known as DDT, is a colorless, tasteless, and almost odorless crystalline chemical compound, an organochloride. Originally developed as an insecticide, it became infamous for its environmental impacts. ...

usage on farms may affect the breeding success of black-billed gulls and herbicides that remain in use could have consequences that are yet unknown. McClellan suggests that climate change could have a positive impact on black-billed gull populations, such as in encouraging earlier or extended breeding seasons, but also a negative impact in increasing food availability, which would result in "poor

synchrony Synchrony may refer to: * Synchronization, the coordination of events to operate a system in unison * Synchrony and diachrony, viewpoints in linguistic analysis * Behavioural synchrony, coordinated action in animals and humans * Synchrony Financi ...

". Nesting on river islands, chicks are also vulnerable to flooding. In a January 2018 flood, a single colony lost up to 2500 chicks. Another colony is thought to have lost around 2200 eggs in a flood in November the same year. In October 2019, Mike Turner responded to a proposal for commercial rafting along the

, citing concerns for the welfare of black-billed gulls.

Conservation efforts

In October 2018, the Department of Conservation began a trial cull of black-backed gulls along the

Hurunui River The Hurunui River is the fourth largest of the four principal rivers in north Canterbury, New Zealand, with a catchment area of . The river flows from the eastern side of the Southern Alps, to the Pacific Ocean. Geography The head of the Hurun ...

to control predation of black-billed gull chicks and other threatened bird species. In August 2019, after a successful trial, the department announced a five-year programme extending to the

Waiau Uwha River Waiau Uwha River, previously known as the Waiau River, is a river in north Canterbury in the South Island of New Zealand. The Waiau Uwha River rises in the Spenser Mountains and flows eastward to the Pacific Ocean. The Waiau Uwha River has the ...

that aims to reduce the black-backed gull population in the areas by at least eighty per cent. The black-billed gull placed 30th, with 441 votes, in Forest & Bird's 2018

Bird of the Year Bird of the Year () is an annual election-based competition run by the New Zealand conservation organisation Forest & Bird to elect a New Zealand native "Bird of the Year". The competition is intended to raise awareness of the conservation thre ...

competition.

Gallery

References

External links

Further images and videos on arkive.org.
{{Taxonbar, from=Q1270731 Chroicocephalus Endemic birds of New Zealand Birds described in 1871 Taxonomy articles created by Polbot Taxobox binomials not recognized by IUCN Taxa named by Frederick Hutton (scientist)