Data Zone
Justification of Red List category
Although the subpopulation on the island of Conception has recently undergone a severe decline, other subpopulations on Frégate Island and Ile du Nord have grown recently, and overall the population is not currently considered to be declining. Nevertheless, the species's population has undergone a moderately severe reduction over the past three generations and its population remains small and limited to a handful of locations, where it is threatened by further rat introductions. Therefore, the species is listed as Vulnerable.
Population justification
The populations on each island have been estimated as follows: c.20 birds on Mahé in 2018, 10 to 15 individuals in Conception in late 2018, c.240 individuals on Frégate Island in 2017, and 125-140 individuals on Ile du Nord (North Island) in 2017 (Pietersen, 2017, Rocamora et al. 2018, G. Rocamora in litt. 2019, IBC-UniSey unpubl.). In 2018, 30 individuals from Frégate Island and 17 individuals from Ile du Nord were translocated to Grande Soeur Island (G. Rocamora in litt. 2019, IBC-UniSey unpubl.). The population on Cousine apparently failed, with no more than five individuals recorded there in 2013 (G. Rocamora in litt. 2014), all of which vanished shortly after (G. Rocamora in litt. 2019, IBC-UniSey unpubl.). The newly-translocated population on Grande Soeur was reported to number c.40-45 individuals and to have produced four fledglings in 2019 (G. Rocamora in litt. 2019). However, since this population was reintroduced less than five years ago, it is not included in the current population estimate. The total population size is estimated at c.340-400 individuals. This roughly equates to 227–267 mature individuals, rounded here to 220–270 mature individuals, with the most likely population size placed at 250 mature individuals.
Trend justification
The population on Mahé was estimated to number c.60 birds in 2006, but declined down to 40 birds in 2011-2013 (G. Rocamora in litt. 2014) and c.20 birds by 2018 (G. Rocamora in litt. 2019, IBC-UniSey unpubl.).
The population on Conception was estimated at c.340 individuals in 2009 (Rocamora and Labiche 2009) and c.310 individuals in 2014 (G. Rocamora in litt. 2019). In 2017 it was discovered that Black Rats Rattus rattus had colonised the island, probably about two years before in view of the rat distribution and abundance observed during visits. Subsequently, the population of Seychelles White-eye on Conception was almost eliminated, estimated at 10 to 15 individuals in late 2018 (G. Rocamora in litt. 2019, IBC-UniSey unpubl.).
The transfer of 37 individuals from Conception to Frégate Island in 2001 and 2003 resulted in the establishment of an estimated population of c.100 individuals there in 2007 (G. Rocamora in litt. 2007, Henriette and Rocamora 2011), c.150 individuals in 2010/2011 (G. Rocamora in litt. 2014) and c.240 individuals in 2017 (G. Rocamora in litt. 2019; Rocamora et al. 2018). Thirty individuals were translocated from Frégate Island to Grande Soeur Island in 2018 (G. Rocamora in litt. 2019, IBC-UniSey unpubl.).
In 2007, 25 birds were transferred to Ile du Nord, and 23 to Cousine (Rocamora and Henriette-Payet 2009). The population on Ile du Nord increased to approximately 100 individuals in 2014 (Havemann and Havemann 2014) and 125-140 individuals in 2017 (Pietersen, 2017), 17 of which were translocated to Grande Soeur Island in 2018 (G. Rocamora in litt. 2019). However, the population on Cousine has apparently failed, with no more than five individuals recorded there in 2013 (G. Rocamora in litt. 2014), all of which vanished shortly after (G. Rocamora in litt. 2019, IBC-UniSey unpubl.).
The translocations to Grande Soeur took place less than five years ago, hence the population there is not included in this assessment.
Combining these figures and assuming linear trends, the overall population size is estimated to have undergone a reduction of between 30% and 49% over the last three generations.
If we assume that ongoing subpopulation trends will continue, the overall population size is projected to increase over the next three generations. Both Frégate and Ile du Nord have been estimated to have carrying capacities of several hundred individuals (Rocamora in litt. 2019), so we assume that these subpopulations will continue to grow.
Over a period of three generations which extends from the past and into the future, the maximum population reduction is estimated to be 30-40%, assuming that current subpopulation trends continue.
This species has populations on the islands of Mahé and Conception in the Seychelles, with translocated populations on Frégate, Ile du Nord (North Island) and since 2018, Grande Soeur Island.
It was previously thought to survive only in three tiny areas on Mahé, and appeared to be declining inexorably towards extinction. In 1996, only 25-35 individuals were known (Rocamora 1997a). In 1997, a previously unknown population, estimated to hold "at least 250" individuals, was discovered on Conception (Rocamora 1997a, Rocamora and Francois 1999), with c.50 more individuals estimated to be present on Mahé (G. Rocamora in litt. 1999).
The population on Mahé was estimated to number c.60 birds in 2006, but declined down to 40 birds in 2011-2013 (G. Rocamora in litt. 2014) and c.20 birds by 2018 (G. Rocamora in litt. 2019, IBC-UniSey unpubl.). It now occurs at only two localities on the island - La Misère and Grande Anse (G. Rocamora in litt. 2019).
The population on Conception was estimated at c.275 (244-336) individuals in 1999, c.230 (189-266) in 2006, c.340 in 2009 (Rocamora and Labiche 2009) and c.310 individuals in 2014 (G. Rocamora in litt. 2019). In 2017 it was discovered that Black Rats Rattus rattus had colonised the island, probably about two years before in view of the rat distribution and abundance observed during visits. Subsequently, the population of Seychelles White-eye on Conception was almost eliminated, estimated at 10 to 15 individuals in late 2018 (G. Rocamora in litt. 2019, IBC-UniSey unpubl.; A Skerret, pers. comm., 2020).
The transfer of 37 individuals from Conception to Frégate Island in 2001 and 2003 resulted in the establishment of an estimated population of c.100 individuals there in 2007 (G. Rocamora in litt. 2007, Henriette and Rocamora 2011), c.150 individuals in 2010/2011 (G. Rocamora in litt. 2014) and c.240 individuals in 2017 (G. Rocamora in litt. 2019; Rocamora et al. 2018). Thirty individuals were translocated from Frégate Island to Grande Soeur Island in 2018 (G. Rocamora in litt. 2019, IBC-UniSey unpubl.).
In 2007, 25 birds were transferred to Ile du Nord, and 23 to Cousine (Rocamora and Henriette-Payet 2009). The population on North Island increased to approximately 100 individuals in 2014 (Havemann and Havemann 2014) and 125-140 individuals in 2017 (Pietersen, 2017), 17 of which were translocated to Grande Soeur Island in 2018 (G. Rocamora in litt. 2019). However, the population on Cousine has apparently failed, with no more than five individuals recorded there in 2013 (G. Rocamora in litt. 2014), all of which vanished shortly after (G. Rocamora in litt. 2019, IBC-UniSey unpubl.).
The newly-translocated population on Grande Soeur was reported to number c.40-45 individuals and to have produced four fledglings in 2019 (G. Rocamora in litt. 2019).
Data from a recent study have suggested that the populations on Mahé and Conception are genetically isolated from each other (<1-2 migrants per generation), and that one does not represent a subsample of the other (Rocamora and Richardson 2003). They probably became isolated following the decline of the Mahé population, caused by human disturbance, 100-200 years ago, and retain different genetic fragments of the original population. The populations on both Mahé and Conception show low levels of genetic variability, comparable with the inbred island populations of other species (Rocamora and Richardson 2003). The ecology of the two populations differ, with individuals on Conception holding territories in dense mixed woodland with an abundance of native fruiting trees, whereas birds on Mahé show flexibility in habitat choice (Rocamora and Richardson 2003).
On Mahé, it is predominantly found in man-made habitats, such as farms, residential areas, orchards, forest edge and mixed secondary forest (Rocamora 1997a), seeming to prefer particular exotic tree and shrub species (Mee 1996, 1997, Rocamora 1997a). It principally eats insects, but also berries and nectar (Rocamora 1997b). On Mahé, its productivity in the 1990s was poor and recruitment very low, and it is possible that more widely dispersed populations have been lost in the past as productivity has declined (Mee 1997, Rocamora 1997a). It is a cooperative breeder, and on Conception breeding groups and clutch sizes have tended to be bigger than on Mahé, with adult birds on Conception also showing low fidelity to particular nests. The trapping of birds has indicated a possible deficit of females on both Mahé and Conception, although the tape luring methods used are more likely to attract males (Rocamora and Richardson 2003).
Loss of native vegetation - particularly large trees - may have been a factor in its decline (Gerlach 1996). However, there is no recent evidence of a significant decline in habitat quantity or quality (R. Bristol in litt. 2004), although invasion by alien plants continues on Mahé (J. Gerlach in litt. 2012). Nest-predation, by the introduced Black Rat Rattus rattus and Common Myna Acridotheres tristis, and the abundant Seychelles Bulbul Hypsipetes crassirostris, is the biggest threat on Mahé (Rocamora 1997a, 1997b, Rocamora et al. 1999, Rocamora and Francois 1999).
In 2017 it was discovered that Black Rats Rattus rattus had colonised Conception, probably about two years before in view of the rat distribution and abundance observed during visits. Subsequently, the population of Seychelles White-eye on Conception was almost eliminated (G. Rocamora in litt. 2019, IBC-UniSey unpubl.). Conception was previously inhabited by R. norvegicus but an eradication operation was conducted in August 2007 (G. Rocamora in litt. 2007). Fire and disease are also threats on Conception (Rocamora 1997a, Rocamora 1997b, G. Rocamora in litt. 2007). Frégate and Ile du Nord have biosecurity procedures in place and have remained rat free since 2000 and 2005 respectively (G. Rocamora in litt. 2019).
Given its extremely small and fragmented range, the species is vulnerable to sudden stochastic events. Health screening done during 2007 transfers revealed the presence of a widespread Microfileria in the Conception population, although presence of such blood parasites in white-eye populations is common and normally not considered a significant threat (G. Rocamora in litt. 2007).
Conservation and Research Actions Underway
None of the species's current sites on Mahé lie within the Morne Seychellois National Park (Mellanby et al. 1996). Predator control and nest monitoring have been conducted on Mahé since 2006, and population monitoring has been carried out on the islands where the species occurs (G. Rocamora in litt. 2007). In 2000, the Ministere de l'Environnement started cat and rat eradication on several islands including Frégate; subsequently, in 2001 and 2003, 37 individuals were transferred to Frégate (Rocamora et al. 2002, G. Rocamora in litt. 2007, Henriette and Rocamora 2011, Millett et. al. 2019), an island which models suggest could support a population of more than 500 individuals (Rocamora et al. 2002). By 2017 there were c.240 birds on the island. Breeding on Frégate extended beyond the normal breeding season indicating favourable conditions on the island. In 2007, 25 individuals were transferred from Conception to Ile du Nord, following successful rat eradication in 2005, whilst 20 were transferred from Conception and three from Mahé to Cousine (G. Rocamora in litt. 2007). Intensive habitat restoration was carried out on both islands (G. Rocamora in litt. 2007). The population on Ile du Nord increased to 125-140 individuals in 2017 (Pietersen, 2017). However, the population on Cousine has apparently failed, with no more than five individuals recorded there in 2013 (G. Rocamora in litt. 2014), all of which vanished shortly after (G. Rocamora in litt. 2019, IBC-UniSey unpubl.). Biosecurity protocols are in place on both Frégate and Ile du Nord (Millett et al. 2019, G. Rocamora in litt. 2019). Common Myna (Acridotheres tristis) has been eradicated from Frégate and work is underway to eradicate it from Ile du Nord (Rocamora 2019). Since 2016, all subpopulations have been monitored as part of the CEPF project, ‘Advancing Ecosystem Management and Threatened Species Recovery through Partnerships with Private sector’ coordinated by the Island Biodiversity and Conservation Centre of the University of Seychelles (IBC-UniSey) (G. Rocamora in litt. 2019). Other project activities have included biosecurity measures on Grande Soeur and rat monitoring and control and habitat restoration on Mahé (Henriette, n.d.). The project team has also worked with schools in La Misère, Mahé to raise awareness of the conservation of Seychelles White-eye (Henriette, n.d.). In 2018, 30 individuals from Frégate Island and 17 individuals from Ile du Nord were translocated to Grande Soeur Island (G. Rocamora in litt. 2019, IBC-UniSey unpubl.). The new population on Grande Soeur was reported to number c.40-45 individuals and to have produced four fledglings in 2019 (G. Rocamora in litt. 2019).
Conservation and Research Actions Proposed
Continue to monitor population trends in all islands occupied by the species (both source and transferred populations). Protect the species's habitat. Encourage preservation of large garden trees in residential areas where the species is present on Mahé to help their short-term survival there (Gerlach 1996, Rocamora 1997a). Continue rat control and protection of nests in the two main Mahé subpopulations (G. Rocamora in litt. 2007, Millett et al. 2019). Eradicate rats on Conception and control rats until this can be achieved (G. Rocamora in litt. 2019). Continue biosecurity measures on Frégate and Ile du Nord. Consider translocation to other suitable predator- and competitor-free islands (Gerlach 1996, Rocamora 1997a, N. J. Shah and S. Parr in litt. 1999, A. Skerrett in litt. 1999). Continue to mix individuals from different source populations during translocations, thus recombining genetic variation in the species (Rocamora and Richardson 2003).
10 cm. Small, dull olive-grey, warbler-like bird. Dark olive-grey upperparts with paler underparts and narrow, white eye-ring. Flank feathers sometimes fluffed open to impart pale grey flank-flash. Tiny, sharp bill. Voice Short, trilling nasal contact call and loud song.
Text account compilers
Clark, J.
Contributors
Adam, P.-A., Ashpole, J, Bristol, R., Ekstrom, J., Gerlach, J., Hardcastle, J., Harding, M., Parr, S., Pilgrim, J., Rocamora, G., Shah, N.J., Shutes, S., Skerrett, A., Symes, A., Taylor, J., Warren, B., Westrip, J.R.S. & Wheatley, H.
Recommended citation
BirdLife International (2024) Species factsheet: Seychelles White-eye Zosterops modestus. Downloaded from
https://datazone.birdlife.org/species/factsheet/seychelles-white-eye-zosterops-modestus on 22/12/2024.
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 22/12/2024.