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Larus bulleri
– Endangered
Taxonomy
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Kingdom:
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ANIMALIA
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Phylum:
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CHORDATA
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Class:
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AVES
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Order:
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CHARADRIIFORMES
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Family:
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LARIDAE
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Scientific Name:
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Larus bulleri
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Species Authority:
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Hutton, 1871
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Common Name/s:
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| English | — | BLACK-BILLED GULL |
| French | — | MOUETTE DE BULLER |
| Spanish | — | GAVIOTA MAORÍ |
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Assessment Information
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Red List Category & Criteria:
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EN A2bce+3bce ver 3.1 (2001)
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Year Assessed:
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2006
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Assessor/s:
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BirdLife International
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Evaluator/s:
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Butchart, S. & Pilgrim, J. (BirdLife International Red List Authority)
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Justification:
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Surveys indicate that this species may have undergone a very rapid decline throughout most of its breeding range, equivalent to an overall decline of more than 50% in 32 years (three generations). It is therefore listed as Endangered.
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History:
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| 1988 | - | Lower Risk/least concern (BirdLife International 2004) |
| 1994 | - | Lower Risk/least concern (BirdLife International 2004) |
| 2000 | - | Vulnerable (BirdLife International 2000) |
| 2004 | - | Vulnerable (BirdLife International 2004) |
| 2005 | - | Endangered (BirdLife International 2005) |
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Geographic Range
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Range Description:
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Larus bulleri is endemic to New Zealand. The majority of the population (78%) breeds in Southland5, mostly on the Mataura, Oreti, Aparima and Waiau rivers4. On the Oreti and Aparima, the number of breeding birds appears to have plummeted by as much as 90% in the last one to two decades4,5. Upper Waitaki catchment populations declined between the 1960s and 1990s, with breeding colonies disappearing from six rivers3. Recent surveys at one minor colony in the Hunter Valley, Otago, showed numbers had dropped from 581 in 1969 to just 12, with the same trend seen in the nearby Makarora catchment area7. Overall, Southland counts estimated a minimum of 57,000 pairs in 1985-19865, declining c.40% to 33,500 pairs in 1996-19974. However, numbers and range continue to increase in the North Island, but these colonies are small and do not offset the South Island declines7. The most complete nationwide census was carried out in 1996-19976, and counted 48,000 nests4. Some birds remain at colonies throughout the year, others move from inland breeding sites to the coasts2.
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Range Map:
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 (click for detailed map)
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Countries:
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Native:
New Zealand (North Is., South Is.)
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Population
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Population Trend:
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Habitat and Ecology
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Habitat and Ecology:
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In the South Island, it breeds mainly on braided river systems2,5. In the North Island, it uses sand-spits, shellbanks, lake margins and riverflats5. It often roosts and feeds on farmland, and scavenges in urban areas where refuse is available2. It has a varied diet of terrestrial, freshwater and marine invertebrates, fish and shellfish1,2. Breeding can begin after two years1, but many individuals do not start until six years old, and adults may live over 30 years7.
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System:
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Terrestrial; Freshwater
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Threats
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Threats:
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Brown rat Rattus norvegicus takes eggs and chicks in the North Island. Mustelids Mustela spp., feral cats and hedghogs may be key predators on South Island riverbeds. Recreational use of riverbeds and coastal areas is increasing, causing greater disturbance of nesting colonies5. River modification (including hydroelectric development, and water and gravel extraction) also has a significant impact. The spread of weeds is a major threat, reducing suitable nesting habitat on riverbeds3,5.
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Conservation Actions
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Conservation Actions:
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Conservation measures underway:
Studies of breeding biology, movements and dispersal are being undertaken. Localised and nationwide counts are ongoing. Habitat restoration and protection in the MacKenzie Basin is undertaken as part of Project River Recovery, including predator research and a public awareness campaign5.
Conservation measures proposed:
Monitor key breeding populations. Initiate nest protection at key colonies if research indicates that breeding success is significantly affected by introduced predators. Initiate riverbed weed control if nesting habitat continues to be lost. Assess possible impact of further hydro-dam, gravel and water extraction proposals5.
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