Data Zone
Justification of Red List category
In 2008 the population increased to be above the Critically Endangered threshold, and the population size has remained >50 mature individuals since then. The species does still inhabit a very small range, and is susceptible to fluctuations, therefore it still warrants listing as Endangered.
Population justification
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), with the population having been >50 mature individuals since 2008. Therefore, the population size is placed here in the range 250-999 mature individuals.
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.
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.
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).
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 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). 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). 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 Charles Darwin Foundation 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 was scheduled for 2014 (Nicholls 2013). Modelling work has been conducted to investigate the best strategy for reintroductions (Bozzuto et al. 2017). 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).
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.
Text account compilers
Khwaja, N., Wright, L, Westrip, J., Isherwood, I., Mahood, S., Calvert, R., McClellan, R., Gilroy, J., Pople, R., Sharpe, C.J., Symes, A.
Contributors
de Vries, T., Tye, A., Wiedenfeld, D., Jiménez-Uzcátegui, G., Hoeck, P.
Recommended citation
BirdLife International (2024) Species factsheet: Floreana Mockingbird Mimus trifasciatus. Downloaded from
https://datazone.birdlife.org/species/factsheet/floreana-mockingbird-mimus-trifasciatus on 27/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 27/12/2024.