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| black-billed gull | |
|---|---|
| Name | Black-billed gull |
| Status | CR |
| Genus | Larus |
| Species | novaehollandiae |
| Authority | (Latham, 1801) |
black-billed gull The black-billed gull is a small, endemic seabird of New Zealand notable for its dark bill and colonial nesting. It is associated with riverine, lacustrine and coastal environments and has been the focus of major conservation concern due to rapid declines. Populations have been monitored by organisations and agencies across New Zealand, prompting involvement by international groups and research programmes.
Described in 1801 by John Latham, the species was placed in the genus Larus and named novaehollandiae reflecting early collectors' associations with New Holland and exploration by figures such as Captain James Cook, Joseph Banks, and Daniel Solander. Taxonomic treatments have referenced works by Charles Darwin, Alfred Russel Wallace, and later avian systematists at institutions including the British Museum (Natural History), the American Museum of Natural History, and the Natural History Museum, London. Molecular studies involving laboratories at University of Oxford, CSIRO, and University of Canterbury have compared mitochondrial markers used by researchers including Avian phylogenetics groups and collaborators at the Smithsonian Institution. Nomenclatural discussion has appeared in checklists curated by the International Ornithologists' Union, the Royal Society of New Zealand, and regional field guides produced by authors affiliated with Victoria University of Wellington and University of Otago.
Adults show a white head and body, grey wings, and a black bill; plumage details have been documented in field guides by Kenneth Parkin and others. Measurements recorded by surveys conducted by the Department of Conservation (New Zealand) and researchers at Landcare Research indicate a wingspan and mass consistent with small gull species measured in comparisons with silver gull, kelp gull, and black-backed gull specimens held at the Canterbury Museum. Detailed plates have been produced in compendia curated by the Royal Society and illustrators working with the National Geographic Society and the Audubon Society. Juvenile and subadult plumages have been described in monographs from the British Ornithologists' Club and field observations by members of the Royal Australasian Ornithologists Union.
The species is endemic to New Zealand and occurs across both the North Island and South Island, with breeding concentrated on braided rivers such as the Makarora River, Waitaki River, and locations near Lake Ellesmere / Te Waihora and coastal sites like Kaikōura and Nelson. Non-breeding movements include estuaries and harbours documented at Auckland Harbour, Otago Harbour, and the Firth of Thames. Habitat studies have involved partnerships with regional councils including the Canterbury Regional Council and conservation projects run by groups such as Forest & Bird and iwi entities including Ngāi Tahu and Te Rūnanga o Ngāi Tahu. Observational records have been contributed to databases maintained by the New Zealand Bird Atlas and international aggregators such as the Global Biodiversity Information Facility.
Gregarious outside the breeding season, colonies show social organisation observed in seabird studies originating with work at University of Auckland, Massey University, and international collaborations with University of Cambridge and University of California, Davis. Roosting and flocking behaviour have been compared in publications in journals associated with the Royal Society and the Ecological Society of America. Movement ecology has been examined using tracking technologies developed at labs such as NIWA and engineering groups at University of Canterbury, with tagging protocols informed by guidelines from the Ornithological Council and monitoring frameworks used by BirdLife International. Predation pressure from introduced mammals has been recorded in studies involving the Department of Conservation (New Zealand), regional pest control programmes coordinated by Zero Invasive Predators (ZIP), and community groups.
Breeding occurs in colonies on braided rivers, islands and coastal sites; timing and success rates have been monitored by researchers from the University of Otago, Massey University, and the Canterbury University School of Biological Sciences. Nesting ecology has been detailed in reports produced for the Conservation Services Programme and by conservation NGOs including Forest & Bird and the Royal Society Te Apārangi. Eggs and chick development have been described in field studies referencing methodologies promoted by the British Trust for Ornithology, and management interventions such as predator control have been implemented in partnership with local iwi including Ngāti Apa and regional conservation trusts like the Otago Peninsula Trust. Climate effects and flood impacts have been modelled by researchers at Victoria University of Wellington and Lincoln University.
Diet consists of aquatic invertebrates, small fish and anthropogenic food sources; foraging behaviour has been compared to that of common gull studies and research by the Fisheries Research Agency. Foraging ecology has been investigated using techniques developed at the Wellington Institute of Technology and laboratories at Landcare Research, with isotope analyses carried out in collaboration with the University of Otago. Scavenging at urban sites such as Wellington and Christchurch has been recorded alongside predation on riverine invertebrates in studies published through partnerships with the Department of Conservation (New Zealand).
Assessed as Critically Endangered by national listings and highlighted in reports by BirdLife International and the IUCN Red List assessments coordinated with the Department of Conservation (New Zealand), the species faces threats from introduced predators including stoat, ferret, rat incursions monitored by pest control programmes inspired by eradication campaigns on Codfish Island / Whenua Hou and Ulva Island. Habitat loss from river modification involving projects by the Ministry of Works and Development (historically) and contemporary river management by regional councils has been implicated, as have human disturbance at sites near urban centres such as Auckland and Dunedin. Conservation actions involve partnerships with NGOs including Forest & Bird, community groups, iwi authorities like Ngāi Tahu, research teams at University of Canterbury, and funding or policy support from the New Zealand Ministry for the Environment and multinational conservation funders. International awareness has been raised through exhibitions and media collaborations with organisations such as the BBC Natural History Unit and the National Geographic Society.