Data Zone
Justification of Red List category
This species was formerly found within an incredibly small range on Aldabra, Seychelles, but it is now Extinct due to predation and habitat alteration by invasive species. It was last recorded in 1983, and searches in 1986 confirmed its extinction.
Population justification
None remain.
Trend justification
Little is known about the exact cause of this species' extinction. The species appears to have always had a severely restricted geographical range (Prŷs-Jones 1979 in Hume 2017, Safford and Hawkins 2013) and consequentially has likely always occurred in low densities. Two individuals were collected in 1967 (Benson and Penny 1968), and another in 1974, with none seen until five were observed through surveys in 1974-76 (Prŷs-Jones 1979). Only two males were known definitively as of February 1977, with only one by October 1983 (Collar and Stuart 1985), which was the last record of the species (Safford and Hawkins 2013). The disappearance of the species was very likely caused by cats and Rattus rattus (Black Rats) which were present on middle island (Hume 2017). A speculated secondary factor was the presence of Aldabrachelys gigantea (Aldabra Giant Tortoise), which generally do not occur in the dense scrub that Nesillas aldabrana occupied (Prŷs-Jones 1979, Safford and Hawkins 2013). However, as introduced goats altered habitat through grazing, the tortoises may have been allowed access to these habitats, and began grazing on leaf litter which N. aldabrana required for foraging (Prŷs-Jones 1979, Safford and Hawkins 2013). Regardless, it appears this poorly known species became extinct sometime in the early 1980s.
Nesillas aldabrana was endemic to Ile Malabar, Aldabra, Seychelles (Hambler et al. 1985). The species was only discovered in 1967 (Benson and Penny 1968), and the last records were in 1983 when it seemed only males remained (Hambler et al. 1985, Skerrett and Disley 2011).
This species occurred in rugged areas of limestone rock, covered by dense mixed scrub (Prŷs-Jones 1979 in Hume 2017, Safford and Hawkins 2013). It was a skulking, insectivorous species (Benson and Penny 1968) which foraged through leaf litter (Prŷs-Jones 1979).
The species always had a very restricted range (Prŷs-Jones 1979 in Hume 2017, Safford and Hawkins 2013), which meant it was always at high risk of extinction. The exact cause of its extinction is uncertain, but cats (direct predation) and Rattus rattus (nest predation) were present on the island and were likely a major threat (Hume 2017). Further, browsing/grazing by introduced goats would have degraded the already restricted habitat for the species (Prŷs-Jones 1979, Safford and Hawkins 2013). Consequentially, this may have allowed access into these habitats for Aldabrachelys gigantea (Aldabra Giant Tortoise), which would have fed on leaf litter, removing a vital habitat feature that N. aldabrana required for foraging (Prŷs-Jones 1979, Safford and Hawkins 2013).
Text account compilers
Khwaja, N., Martin, R., Mahood, S., Brooks, T., Richardson, L.
Recommended citation
BirdLife International (2024) Species factsheet: Aldabra Brush-warbler Nesillas aldabrana. Downloaded from
https://datazone.birdlife.org/species/factsheet/aldabra-brush-warbler-nesillas-aldabrana on 23/12/2024.
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 23/12/2024.