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Black-backed gull

Braided River Status

Found on or over all non-forested habitats from coastal waters to high-country farms, it is abundant along all braided rivers.

Description

The Southern black-backed gull (Larus dominicans) karoro, (Maori), also known as the kelp gull, Dominican gull, mollyhawk, and seagull, is the largest gull and one of the most abundant large birds in New Zealand. It is also common in southern Australia, South America, southern Africa, most sub-antarctic Antarctic islands and the Antarctic Peninsula. Adults have white head and underparts with black back, yellow bill with red spot near tip of lower mandible, and pale yellow-greenish legs. Juveniles are dark mottled brown with black bill and legs; their plumage lightens with age until they moult into adult plumage at 3 years old. Juveniles may be confused with the stockier brown skua.

Black-backed gull photo : Phillip Capper
Black-backed gull  and chicks – photo by Phillip Capper

Why is it a problem?

A scavenging bird, their population exploded as a direct result of human activities, primarily around garbage dumps, fish processing plants, and areas where effluent is discharged. While their populations have declined somewhat in the past few years as rubbish disposal has been improved, like all scavengers, they are opportunistic predators that readily kill river bird chicks – see the video below – and are increasingly implicated in the failure of entire breeding colonies of critically endangered endemicblack-billed gulls.

Conservation activities

The black-backed gull is one of only two native bird species not afforded any level of protection under the Wildlife Act. Black-backed gulls are often considered pests and on farmland, where some attack cast sheep and newborn lambs. As a result, they are sometimes shot, or controlled using toxins or by pricking their eggs. At a few sites, including the Waimakariri River and Hurunui River,  they are controlled to reduce their predatory impacts on threatened birds.

A draft ‘issues and options’ report for controlling the population in areas where endangered and critically endangered braided river bird species was completed in late 2018 after public consultation. The final strategy is expected to be completed in 2019.

The voracity of black-backed gulls is evident: yes, this is in fact a rabbit being gobbled down

Important: in spite of their size, they are sometimes mistaken for the critically endangered black-billed gull or the declining red-billed gull. To avoid fines up to $300,000 for mistaken identity, any attempt to control black-backed gulls through shooting, trapping, poisoning, pricking eggs, or any other method,  should only be undertaken after consulting with ECan or DOC in your area.

More information

Research papers

Schlesselmann, A. (2018) Linking science and management for effective long-term conservation: A case study of black-fronted terns/tarapirohe (Chlidonias albostriatus)(Thesis, Doctor of Philosophy). University of Otago

Boothby, C et al (2018) An evaluation of canes as technique to reduce predation by gulls on ground nesting seabirds.

Schlesselmann, A. (2018) Linking science and management for effective long-term conservation: A case study of black-fronted terns/tarapirohe (Chlidonias albostriatus)(Thesis, Doctor of Philosophy). University of Otago.

Fordham, R.A. and R. M. Cormack (1970), Mortality and Population Change of Dominican Gulls in Wellington, New Zealand: With a Statistical Appendix  Journal of Animal Ecology  Vol. 39, No. 1 (Feb., 1970), pp. 13-27 DOI: 10.2307/2887

Wilkinson, G.B .(1992)  PhD thesis, University of Canterbury; ‘Some aspects of the breeding biology of the Dominican gull Larus dominicanus (Lichtenstein 1823) in Nelson province, New Zealand’.

Harris, M. & S. Wanless (1997) The effect of removing large numbers of gulls Larus spp. on an island population of oystercatchers Haematopus ostralegus: implications for management. Biological Conservation 82 (1997) 167-171

Yorio, P. et al (1998)  Kelp Gulls Larus Dominicans breeding on the Argentine Coast: population status and relationship with coastal management and conservation Fundación Patagonia Natural and Wildlife Conservation Society, M. A. Zar 760, 9120 Puerto Madryn, Chubut, Argentina.

Bosch, M. et al (2000) Short-term effects of culling on the ecology and population dynamics of the yell-legged gull. British Ecological Society Journal of Applied Ecology, 37

Guillemette, M & P Brousseau (2001) Does culling predatory gulls enhance the productivity of breeding common terns? Journal of Applied Ecology 200138, 1–8

Donehoer et al, (2007) Effect of Gull Predation and Predator Control on Tern Nesting Success at Eastern Egg Rock, Maine. Waterbirds 30(1): 29-39, 2007

Oro, D. & A. Martinez-Abrain (2007) Deconstructing myths on large gulls and their impact on threatened sympatric waterbirds Animal Conservation 10 (2007) 117–126

Lisnizer, N.A. et al (2011), Spatial and temporal variation in population trends of Kelp Gulls in northern Patagonia, Argentina; Emu 111(3) 259-267 https://doi.org/10.1071/MU11001

Galbraith, M. et al (2015) Changes in the breeding status of the southern black-backed gull (Larus dominicanus) colonies on Rangitoto Island, Hauraki Gulf, New Zealand. Notornis, 2015, Vol. 62: 192-201

Nelson, P. Bird (1994) Control in New Zealand using Alpha-Chloralose and DRC1339. Proceedings of the Sixteenth Vertebrate Pest Conference (1994). 40.http://digitalcommons.unl.edu/vpc16/40

Chapuis, et al. ( 2001) Eradication of rabbits (Oryctolagus cuniculus) by poisoning on three islands of the subantarctic Kerguelen Archipelago, Wildlife Research 28(3) 323 – 331, https://doi.org/10.1071/WR00042

Cooke et al (2004) Potential use of myxoma virus and rabbit haemorrhagic diseas virus to control feral rabbits in the Kerguelen Archipelago. CSIRO Wildlife Research 03084 2007  http://www.publish.csiro.au/journals/wr

Rattner, BA, and FN Mastrota (2017) Anticoagulant Rodenticide Toxicity to Non-target Wildlife Under Controlled Exposure Conditions  Anticoagulant Rodenticides and Wildlife pp 45-86 https://link.springer.com/chapter/10.1007/978-3-319-64377-9_3

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