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Mimus trifasciatus 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Passeriformes Mimidae

Scientific Name: Mimus trifasciatus (Gould, 1837)
Common Name(s):
English Floreana Mockingbird, Charles Mockingbird
Synonym(s):
Nesomimus trifasciatus (Gould, 1837) — BirdLife International (2004)
Orpheus trifasciatus Gould, 1837
Taxonomic Source(s): del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A., Fishpool, L.D.C., Boesman, P. and Kirwan, G.M. 2016. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 2: Passerines. Lynx Edicions and BirdLife International, Barcelona, Spain and Cambridge, UK.
Identification information: 25 cm. Largish, brown passerine. Dark brownish-grey upperparts. Whitish underparts with conspicuous dark patches on sides of breast. Long, graduated tail with pale tips. Longish, curved beak. Red-brown eyes. Voice Strident call. Long, melodious song. Does not mimic other birds.

Assessment Information [top]

Red List Category & Criteria: Critically Endangered D ver 3.1
Year Published: 2016
Date Assessed: 2016-10-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): Hoeck, P., Jiménez-Uzcátegui, G., Tye, A., Wiedenfeld, D. & de Vries, T.
Facilitator/Compiler(s): Calvert, R., Gilroy, J., Isherwood, I., Mahood, S., McClellan, R., Pople, R., Sharpe, C J, Symes, A., Khwaja, N. & Wright, L
Justification:
This species is classified as Critically Endangered because it has a tiny population. Numbers fluctuate owing to extreme weather, and in 2008 the population increased to be above the Critically Endangered threshold. If the population remains at this level for more than five years, or if reintroduction efforts prove successful, the species may be downlisted in the future.

Previously published Red List assessments:

Geographic Range [top]

Range Description:This species survives in low numbers on Champion (0.1 km2) and Gardner-by-Floreana (0.8 km2) islets in the Galápagos Islands, Ecuador (Grant et al. 2000). It became extinct on the much larger Floreana (173 km2) between 1868 and 1880 (Curry 1986, Steadman 1986). In 1966, the population was estimated to be no more than 150 birds (Harris 1968). Between 1980 and 1991, annual counts showed that there were 8-12 (average 10) territories on Champion, with 24-53 birds in total (Grant et al. 2000). On the same island between 2003 and 2008, numbers of birds varied from 20-52, but overall there was a downward population trend with 12 adults left in 2006 (Charles Darwin Foundation 2007b, Jiménez-Uzcátegui et al. 2011). A similar trend was noted on Gardner-by-Floreana during the same period, with the number of birds on that island varying between 65 and 179, and the number of adults in 2007 falling to 29 (Charles Darwin Foundation 2007b, Jiménez-Uzcátegui 2007, Jiménez-Uzcátegui et al. 2011). The population recovered in 2008 due to good weather conditions and may have reached record numbers for the last decade, however such population highs are likely only to be temporary as the islands cannot support such numbers and the populations are still extremely prone to climate-induced fluctuations (Hoeck 2009, Charles Darwin Foundation in litt. 2009, D. Wiedenfeld in litt. 2010). 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.

Countries occurrence:
Native:
Ecuador (Galápagos)
Additional data:
Estimated area of occupancy (AOO) - km2:1Continuing decline in area of occupancy (AOO):No
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:17
Continuing decline in extent of occurrence (EOO):NoExtreme fluctuations in extent of occurrence (EOO):No
Number of Locations:2Continuing decline in number of locations:No
Extreme fluctuations in the number of locations:No
Upper elevation limit (metres):50
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:Between 2003 and 2008, the population on Champion Island numbered 20-52 individuals, with 65-179 on Gardner-by-Floreana. Both populations reached lows in 2007 following very bad weather conditions in 2006, with a total population of just 46 mature individuals remaining. Numbers then recovered in 2008 due to good, wet weather conditions (D. Wiedenfeld in litt. 2010) and in 2012 142 birds were counted (Ortis-Catedral 2012c). The total population was estimated to be 756, based on bird counts in 2012 (Charles Darwin Foundation 2013). However, given that the population undergoes major fluctuations, a population band of fewer than 50 mature individuals is precautionarily retained.

Trend Justification:  The population on both islands declined between 2003 and 2007, with just 48 adults remaining in 2007. Wet weather conditions in 2008 caused the population to rebound (Hoeck, 2009, D. Wiedenfeld in litt. 2010), indicating the population is fluctuating. The increased frequency of dry years could mean a decreasing in the future, however this may be mitigated by the successful reintroduction of the species to Floreana Island.

Current Population Trend:Stable
Additional data:
Number of mature individuals:1-49Continuing decline of mature individuals:No
Extreme fluctuations:YesPopulation severely fragmented:No
No. of subpopulations:2Continuing decline in subpopulations:No
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:No

Habitat and Ecology [top]

Habitat and Ecology:It inhabits the large cactus Opuntia megasperma and other stands of vegetation, including Parkinsonia, Croton and Cordia (Curry 1986). It feeds mostly on terrestrial insects, but also takes arboreal insects, fruit, nectar, pollen, centipedes, crabs, lizards and regurgitated food of boobies Sula spp. It is a cooperative breeder, with a variable mating system (Curry and Grant 1991). A recent study found that the nectar and pollen of Opuntia megasperma is an important food source and nestlings were principally fed Lepidopteran caterpillars (Ortiz-Catedral 2014).

Systems:Terrestrial
Continuing decline in area, extent and/or quality of habitat:No
Generation Length (years):5.3
Movement patterns:Not a Migrant

Threats [top]

Major Threat(s): Extinction on Floreana was probably caused by the depredations of introduced Black Rats (Rattus rattus), feral cats and feral dogs, with introduced goats causing habitat loss (Harris 1973, Curry 1986, Grant et al. 2000). Higher adult mortality occurs in the unusually dry La Niña years (Grant et al. 2000); dry years are increasing in frequency, and this is thought to be driving fluctuations in the population size (as seen in 2007 and 2008) which leave the species prone to extinction (D. Wiedenfeld in litt. 2010). The Smooth-billed Ani (Crotophaga ani) is known to predate other bird species on the archipelago and has been seen on Champion and Gardner-by-Floreana (G. Jiménez-Uzcátegui in litt. 2007). Increased mortality on Champion during the 1982-1983 El Niño event is thought to have been the result of avian pox virus (Grant et al. 2000), and the invasive parasite (Philornis downsi) has been recorded (Wiedenfeld and Jimenez-Uzcategui 2008). Transmission of diseases from domestic chickens could also pose a threat (Deem et al. 2012). There are black rats present on nearby islets whose accidental introduction to either of the breeding islands poses an ever present threat (G. Jiménez-Uzcátegui in litt. 2007). 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 diversity (Grant et al. 2000, Hoeck et al. 2009) although there appears to be no link between inbreeding and immunocompetence within the species (Hoeck and Keller 2012).

Conservation Actions [top]

Conservation Actions: Conservation and Research Actions Underway
A 10-year action plan was developed in 2007, with plans to take active measures to safeguard existing populations, and to create suitable conditions for reintroduction to Floreana (Charles Darwin Foundation 2007b, G. Jiménez-Uzcátegui in litt. 2007, Anon. 2008a). Unauthorised access to both the islands where the species is present is not permitted and there are stringent quarantine measures in place for field gear and researchers (Charles Darwin Foundation 2013). A ringing study is on-going to determine survival rates of the species; another study aims to assess the impacts of the parasite Philornis downsi on the mockingbird population (Ortis-Catedral 2012). The reintroduction plan is supported by an emergency plan, to enable rapid response to critical downward population trends (Anon. 2008b), the Introduced Rodent Eradication Program initiated in 2007 and the initiation of Project Floreana, aimed at the restoration of the island (Anon. 2008a). 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 Site (Jackson 1985).

The Charles Darwin Foundation is plans to reintroduce the species to Floreana, however no translocation occurred in 2010 as an El Niño event was expected which would have made rat and cat control on the island very difficult (P. Hoeck in litt. 2010, G. Jiménez-Uzcátegui in litt. 2012).  In 2012 plans were made to establish a rat- and cat-proof perimeter around Punta Cormorant, a 51 ha peninsula with lowland vegetation on the east side of Floreana Island, either through natural recolonisation from Champion (c.4 km away) or through translocations (Ortis-Catedral 2012b,c,d). However due to the likely impacts of poisoned bait on the mockingbirds it has been decided that a translocation should only take place once Floreana has been fully eradicated of rats and cats (Ortiz-Catedral 2013). Plans have been developed to remove rats from the island and is scheduled for 2014 (Nicholls 2013).  A week-long education campaign took place on Floreana in July 2012 and included events focused on the species (Ortis-Catedral 2012c). In addition, in 2014, children at a local school performed a play about the daily lives of mockingbirds and the importance of keeping Champion and Gardner free of invasive species (Ortiz-Catedral et al. 2014).

Conservation and Research Actions Proposed
Monitor populations and environmental conditions on both islands, preferably annually (Grant et al. 2000). Minimise the risk of chance introductions of predators and disease. Support the establishment of captive-breeding populations and reintroduce to Floreana if eradication of rats, cats, anis, pigs, goats and donkeys is successful. Investigate possibility of reintroduction to other islets, or areas of Floreana, where black rats and cats are absent (G. Jiménez-Uzcátegui in litt. 2012). As Opuntia megasperma appears to be an important food source during the breeding season, it is important to both establish if it is key for breeding and consider a supplementary feeding programme for future reintroductions (Ortiz-Catedral 2014). In addition improved biosecurity measures should be implemented and mockingbirds should only be reintroduced in areas far from poultry and humans (Deem et al. 2012).


Citation: BirdLife International. 2016. Mimus trifasciatus. The IUCN Red List of Threatened Species 2016: e.T22711063A94276031. . Downloaded on 24 October 2017.
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