|Scientific Name:||Terpsiphone corvina|
|Species Authority:||(Newton, 1867)|
|Red List Category & Criteria:||Critically Endangered B1ab(iii) ver 3.1|
|Reviewer/s:||Butchart, S. & Taylor, J.|
|Contributor/s:||Bristol, R., Currie, D., Groombridge, J., Parr, M. & Shah, N.|
This species qualifies as Critically Endangered since it has an extremely small range and probably only one viable population persisting on an island where there has been a continuing decline in the extent of habitat. However, the situation may be improving as this population appears to have substantially increased in the last 20 years, at least partly owing to a variety of habitat management measures. The species may be more adaptable than its present range suggests as a number of territories are now in open woodland with housing encroachment, and an increasing number of tree species are used for nesting. Following the successful reintroduction of birds to Denis Island, this species will warrant downlisting after five years if both populations are still self-sustaining, as the species occurs at multiple locations; but in the meantime it retains this classification as a precautionary measure.
|Range Description:||Terpsiphone corvina was thought to remain only on western La Digue, Seychelles. A few birds have been found on neighbouring Marianne (Ladoucer 1997, Neufeld 1998), although this, along with birds on Praslin (Rocamora 1997a), may represent a non-viable overspill (Parr 1998b) and birds seem unable to establish populations on these neighbouring islands (R. Bristol in litt. 2007, 2008). Sightings on Félicité have also been reported (S. Parr and N. J. Shah in litt. 1999). Comprehensive surveys on La Digue show that the population is increasing: 69-83 pairs (c.150-200 birds) in 1995-1996 (Rocamora 1997a), 104-139 pairs in 2000 (Currie et al. 2002). The translocation of 23 adult birds to Denis Island was conducted in November 2008, with the hope of eventually establishing a population of 40-50 birds on the island (N. J. Shah in litt. 2000, 2008). The first chick successfully fledged on Denis Island in 2009 (BirdLife International 2009).|
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The population is estimated to number 210-278 individuals, roughly equating to 140-190 mature individuals.|
|Habitat and Ecology:||It requires mature stands of indigenous badamier Terminalia catappa and takamaka Calophyllum innophylum trees (Watson 1981, 1991, Currie et al. 2003). It appears to be strictly insectivorous, and birds can breed at one year of age (Currie et al. 2002). Nesting was generally believed to be dependent on a proximity to wetland areas (Rocamora 1997a). However there is a non-random association between surviving native plateau forest and wetland areas (Currie et al. 2002). Native high canopy plateau forest is important for both nesting and foraging: territories are generally smaller where native tree density is high (Currie et al. 2002). The species occurs densely (60% of all territories) on the forested (typically high canopy) plateau areas of La Digue. It is not observed in areas of native (low canopy) dry forest (Currie et al. 2003).|
Alarming rates of habitat loss and fragmentation, due to tourism and private housing developments, may be the greatest threats on La Digue (Gerlach 1996, S. Parr and N. J. Shah in litt. 1999). A wilt disease affecting C. innophylum has lead to increased woodland clearance on the La Digue plateau (Currie et al. 2003). Plants such as water lettuce Pirtia stratiotes, introduced to La Digue's marshes, may possibly have reduced favoured invertebrate prey (Gerlach 1996), although this is unproven. Alien mammals and also some endemic bird species have recently been shown to be nest predators, although T. corvina can resist their impacts more effectively than other endemic birds in the Seychelles (Currie et al. 2002, Currie et al. 2003, Currie et al. 2005). The level of nest predation is highest at the forest edge (Currie et al. 2005), compounding the already negative impact of habitat fragmentation.
Conservation Actions Underway
A 0.1 km2 area of mature woodland was established as a nature reserve on La Digue in 1991 (Shah 1995). Wardening staff have been recruited, a few pools established to increase standing water, an education centre constructed, and public awareness programmes initiated (Shah 1995, Rocamora 1997a). This population was surveyed in 2007 and productivity is routinely monitored. A further 13 ha of marshland was purchased in 2002 increasing the reserve to 21 ha. Pollution monitoring has been ongoing for some time (S. Parr and N. J. Shah in litt. 1999)- a sluice gate was built to protect water quality in the wetland (Shah 1995) and the groundwater supply was protected when a new landfill site was established (Shah 1996). The introduced P. stratiotes is routinely removed from marshland (S. Parr and N. J. Shah in litt. 1999). A programme was completed to assess the best islands to which future translocations could be considered (Currie et al. 2003, N. J. Shah in litt. 2000, 2008). Habitat restoration is ongoing on the now predator-free Denis Island (R. Bristol in litt. 2007, 2008), and this has been accompanied by a 'social marketing' campaign to raise awareness on La Digue (Anon 2007, R. Bristol in litt. 2007, 2008). 23 individuals were translocated to Denis Island from La Digue in November 2008, and the first chick successfully fledged in 2009 (BirdLife International 2009). These efforts were carried out during a three-year project funded by the Darwin Initiative and implemented by a partnership of NGOs and the Ministry of Environment and Natural Resources titled Investing in island biodiversity: restoring the Seychelles Paradise Flycatcher. A follow up social marketing project began in 2011 funding through Birdlife Preventing Extinctions Programme
Conservation Actions Proposed
Complete reintroduction onto Denis. Conserve woodland habitat on La Digue, and consider replanting native forest (Currie et al. 2003). Reforestation should focus on large patches to minimise the level of predation (Currie et al. 2005). Continue population and nest monitoring and research into territory quality and food requirements (Shah 1996, S. Parr and N. J. Shah in litt. 1999). Assess the impact of habitat loss, predation and historical changes in land-use (Shah 1996). Encourage placement of new development away from the western plateau or in areas with no existing woodland (Rocamora 1997a, Neufeld 1998). Continue removal of invasive water plants on La Digue (Gerlach 1996, S. Parr and N. J. Shah in litt. 1999). Consider future translocation to a suitable large island with a large area of suitable high canopy (damp) plateau forest eg Praslin or Silhouette (despite the presence of alien and native adult and nest predators), if translocation of flycatchers to Denis continues to prove successful (Currie et al. 2003, D. Currie in litt. 2012).
|Citation:||BirdLife International 2012. Terpsiphone corvina. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 20 May 2013.|
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