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Nesomimus trifasciatus
– 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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PASSERIFORMES
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Family:
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MIMIDAE
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Scientific Name:
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Nesomimus trifasciatus
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Species Authority:
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(Gould, 1837)
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Common Name/s:
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FLOREANA MOCKINGBIRD (Eng)
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Assessment Information
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Red List Category & Criteria:
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EN D ver 3.1 (2001)
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Year Assessed:
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2004
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Assessor/s:
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BirdLife International
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Evaluator/s:
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Pople, R. & Butchart, S. (BirdLife International Red List Authority)
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Justification:
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This species has a very small population on two tiny islands and, as such, it is classified as Endangered. It is regularly affected by extreme weather events, which cause significant changes in the size of the population. If these fluctuations are considered sufficiently extreme, the species should be uplisted to Critically Endangered.
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History:
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| 1988 | - | Lower Risk/least concern (BirdLife International 2004) |
| 1994 | - | Endangered (Collar, Crosby and Stattersfield 1994) |
| 2000 | - | Endangered (BirdLife International 2000) |
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Geographic Range
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Range Description:
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Nesomimus trifasciatus survives in low numbers on Champion (0.1 km²) and Gardner-by-Floreana (0.8 km²) islets in the Galápagos Islands, Ecuador3. It became extinct on the much larger Floreana (173 km²) between 1868 and 18881. In 1966, the population was estimated to be no more than 150 birds4. Between 1980 and 1991, annual counts showed that the number of territories on Champion varied from eight to 12, averaging 10, while total numbers ranged from 24-53 birds3. The status of the Gardner population is less well known - it is estimated to number 150 to 200 birds3. A population viability analysis of the Champion population suggested that there is less than a 50% chance of the bird persisting on the island for another 100 years.
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Countries:
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Native:
Ecuador (Galápagos)
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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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It inhabits the large cactus Opuntia megasperma and other stands of vegetation, including Parkinsonia, Croton and Cordia1. It feeds mostly on terrestrial insects, but also takes arboreal insects, fruit, nectar, pollen, centipedes, crabs, lizards and regurgitated food of boobies Sula spp.2. It is a co-operative breeder, with a variable mating system2.
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System:
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Terrestrial
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Threats
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Threats:
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Extinction on Floreana was probably caused by the introduction of black rat Rattus rattus1. Higher adult mortality occurs in the unusually dry La Niña years3. Increased mortality on Champion during the 1982-1983 El Niño event is thought to have been the result of avian pox virus3. The loss of immigration from the now extinct Floreana population has raised concerns for the long-term survival of the two remaining populations, as they are believed to have lost a significant amount of genetic diversity3.
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Conservation Actions
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Conservation Actions:
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Conservation measures underway:
The Galápagos National Park was gazetted in 1959, and includes almost all the land area of the islands. In 1979, the islands were declared a World Heritage Site5.
Conservation measures proposed:
Monitor populations and environmental conditions on both islands, preferably annually3. Further assess the stability and viability of both populations, using computer modelling of population demography3. Minimise chance introductions of predators and disease. Eradicate goats and, if technology allows, R. rattus from Floreana. Investigate reintroduction to Floreana if R. rattus eradication is successful.
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