Justification of Red List Category
Following the successful translocation to Denis Island, the range and population size have increased steadily and consistently during the last five years, and this species therefore no longer qualifies as Critically Endangered. Both populations on Denis and La Digue islands are now self-sustaining and breeding successfully. The population on La Digue remains threatened by development pressures, which although slowing, are still causing territory loss in some areas of the island. This species has therefore been downlisted to Vulnerable.
The population is now estimated to number between 350-506 mature individuals across both viable populations (280-436 on La Digue and 70 on Denis Island), with the population believed to be increasing on both islands (Bristol et al. 2018, Bristol and Gamatis 2017). Translocations to a third island, Curieuse, began in December 2018.
Until 2008, Terpsiphone corvina was thought to remain only on western La Digue, Seychelles. A few birds were found on neighbouring Marianne (Ladoucer 1997, Neufeld 1998), although this, along with birds on Praslin (Rocamora 1997), may represent a non-viable overspill (Parr 1998) 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), with 2 birds regularly seen there since 2015 (R. Bristol pers. comm. 2020). Regular comprehensive surveys on La Digue show that the population has been steadily increasing: from 150-200 birds in 1996 (Rocamora 1997) to 294-441 birds in 2017 (R. Bristol in litt. 2019). In 2008, 23 adults were translocated to Denis Island to establish a sub-population there. This has become self-sustaining, and now numbers 84 individuals (R. Bristol in litt. 2019). Translocations to Curieuse Island began in December 2018 in an effort to establish a third sub-population there (Fleming 2019), and while they have bred successfully, it remains too early to tell whether that population is self-sustaining (R. Bristol pers. comm. 2020).
It requires mature stands of indigenous badamier Terminalia catappa and takamaka Calophyllum innophylum trees (Watson 1981, 1991; Currie et al. 2003a, 2003b). It feeds on insects and spiders, and birds can breed at one year of age (Currie et al. 2002, Safford 2013). It can breed year-round, and clutches appear to only consist of one egg (Safford 2013). 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 is now breeding in most forest across La Digue, however the breeding success rate is lower in upland territories than on lowland plateau territories (Bristol 2013).
The nature and severity of threats to this species are still poorly understood. Destruction of native broadleaved woodland on is thought to be the primary driver of historical declines and remains a threat on La Digue as a consequence of private house development, agriculture, and demand for timber (Safford 2013). The rate of development has now slowed, but territories are still being lost as a result of development pressure on the western plateau of La Digue (Gamatis and Bristol 2018). Population growth since at least 1988, especially in areas on mountainside off the plateau, make the continued impact of this threat unclear, though (D. Currie in litt. 2019). An increase in public awareness and a ban on catapults in 1991 are thought to have contributed to this recovery (D. Currie in litt. 2019). Though the species is vulnerable to nest predation from non-native predators, particularly at forest edges, it can apparently experience population growth despite these pressures (Currie et al. 2005). The impact of takamaka (Calophyllum inophyllum) wilt disease as well as that of non-native plant species remains unquantified (D. Currie in litt. 2019).
Conservation and Research Actions Underway
This species's population is regularly monitored (Bristol et al. 2018). 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 1997). A further 13 ha of marshland was purchased in 2002 to increase the reserve to 21 ha, however this has never been officially included in the reserve (R. Bristol pers. comm. 2020), and so its level of protection is unclear. 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. 2003a; 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. An education and advocacy campaign has also been carried out (Anon. 2012). A further population of 26 individuals was introduced to Curieuse Island in 2018-2019, and while they have bred successfully, it remains too early to tell whether that population is self-sustaining (R. Bristol pers. comm. 2020).
Conservation and Research Actions Proposed
Conserve woodland habitat on La Digue, and consider replanting native forest (Currie et al. 2003c). 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, Henriette and Laboudallon 2011). 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 1997, Neufeld 1998). Continue removal of invasive water plants on La Digue (Gerlach 1996, S. Parr and N. J. Shah in litt. 1999). Restore more areas of forest on Denis to prevent habitat availability becoming a limiting factor of the population there. Continue control and eliminate myna birds from Denis (Henriette and Laboudallon 2011).
20 cm (plus 16 cm central tail feathers in male). Long-tailed, all-black flycatcher. Male has blue bill and facial skin, long central tail feathers and all-black plumage which, at close range, shows deep blue sheen. Female and juvenile lack long tail feathers and have black head, creamy-white underparts and chestnut upperparts and tail. Voice Harsh szzweet alarm and whistled song.
Text account compilers
Bird, J., Bristol, R., Calvert, R., Currie, D., Ekstrom, J., Groombridge, J., Parr, M.J., Pilgrim, J., Shah, N.J., Shutes, S., Symes, A., Warren, B., Westrip, J.R.S. & Wright, L
BirdLife International (2022) Species factsheet: Terpsiphone corvina. Downloaded from http://www.birdlife.org on 29/11/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 29/11/2022.