Southern black-backed gull
Larus dominicanus Lichtenstein, 1823
New Zealand status: Native
Conservation status: Not Threatened
Other names: karoro, kelp gull, dominican gull, black-backed gull, mollyhawk, seagull, blackbacked gull, black backed gull
Geographical variation: Five subspecies recognised; New Zealand birds are of the subspecies dominicans.The southern black-backed gull (or ‘black-back’) is one of the most abundant and familiar large birds in New Zealand, although many people do not realise that the mottled brown juveniles (mistakenly called “mollyhawks”) are the same species as the immaculate adults. Found on or over all non-forested habitats from coastal waters to high-country farms, this is the only large gull found in New Zealand. They are particularly abundant at landfills, around ports and at fish-processing plants.
Known widely as ‘kelp gull’ in other countries, the same species is also common in similar latitudes around the southern hemisphere, including southern Australia, South America, southern Africa, and most subantarctic and peri-Antarctic islands, and the Antarctic Peninsula.
The familiar large gull throughout New Zealand. Adults have white head and underparts with black back, yellow bill with red spot near tip of lower mandible, and pale green 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.
Voice: a long series of loud calls ‘ee-ah-ha-ha-ha’ etc, given in territorial and aggressive contexts.
Similar species: adults unmistakeable apart from possible vagrant Pacific gull from Australia (which has a more massive bill, and a black subterminal tip to tail). Juveniles may be confused with the more robust brown skua, which has broader wings with a pale flash at the base of the primaries.
Distribution and habitat
Throughout New Zealand in most habitats other than forest and scrub. Abundant anywhere food scraps, offal and other organic waste can be obtained, including landfills and wharves. Common in estuaries and harbours, rocky and sandy shores and riverbeds; occurs more sparsely inland over farmland, and even subalpine tussockland and herbfields. The largest breeding colonies are on islands, steep headlands, sand or shingle spits, or on islands in shingle riverbeds. Breeds on most outlying islands; vagrant to Kermadec Is and Ross Sea.
Very abundant: hundreds of colonies throughout the country, many exceeding 100 pairs, and a few exceeding 1000 pairs. Often gathers in large feeding and roosting flocks.
Ecological and economic impacts
One of only two native bird species not afforded any level of protection under the Wildlife Act. Black-backed gulls are often considered pests, especially at airports (where they are a major cause of bird-strike), 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, they are controlled to reduce their predatory impacts on threatened shorebirds, e.g. New Zealand dotterel, shore plover and fairy tern.