Justification This species is listed as Near Threatened because it has a very small population, which occupies a small range. The species is threatened by introduced and native predators. However, there is no evidence of a decline in the population at present.

Family/Sub-family Dicruridae

Species name author (Ridgway, 1893)

Taxonomic source(s) Dowsett and Forbes-Watson (1993), Sibley and Monroe (1990, 1993)

Population estimate

Population trend

Range estimate (breeding/resident)

Country endemic?

1,500

unset

-

Yes

Range & population Dicrurus aldabranus is found on all four main islands of the Aldabra atoll and neighbouring islets, Seychelles^1,5, and also on the larger lagoon islands of Ile Esprit (where breeding has been reported), Ile Moustique, Gros Ilot, Ile Michel and Ile aux Cèdres^2,5. Its extent of occurrence is less than 150 km^{2 3}. In 1983, the total population was estimated at c.1,500 individuals. It is widely distributed but generally uncommon³.

Important Bird Areas Click here to view map showing IBAs where species is recorded and triggers any of the IBA criteria.

Ecology: This species frequents mixed scrub, mangroves and Casuarina coastal forest^1,3,4,5, but prefers to breed in the latter two habitats, perhaps because the taller trees provide better nesting sites⁵. Territory size ranges from 2.25 ha in Casuarina woodland to 4.5 ha in mixed scrub⁵. It feeds mainly on a variety of insects and small vertebrates such as geckos. Breeding has been recorded between October-November and March-May, and is timed to coincide with the rainy season from December to March. Its nest, in which 1-3 eggs are laid, is a perfectly round cup made from intertwined fine plant fibres bound with spider webs, situated in a fork near the end of a thin horizontal branch, usually 2-8 m above the ground. The species usually nests in tall trees such as Casuarina and mangroves (e.g. Rhizophora mucronata), but also in Ficus spp. in scrub. The incubation period is 16-18 days, followed by a fledging period of 15-19 days. Juvenile birds are dependent for at least several weeks after fledging, and then remain with their parents until at least the following breeding season⁵.

Threats It has a high rate of nest failure, probably largely due to introduced predators⁵. Up to 8/10 studied nests are predated at the egg stage, mainly by crows Corvus spp., rats and bulbuls (Pycnonotidae), as observed or suggested by artificial nest experiments⁵. There are no known threats to its habitat, but its small range and population put it at risk from catastrophic events, such as disease or cyclones⁵.

Conservation measures underway Aldabra is protected as a nature reserve under Seychelles legislation⁵.

Conservation measures proposed Conduct surveys to obtain an up-to-date population estimate. Monitor population trends through regular surveys. Eradicate introduced predators⁵ and exclude native predators from nest-sites. Protect additional habitat on other islands and islets.

References 1. Penny (1974). 2. A. Skerrett in litt. (1999) 3. Stoddart and Westoll (1979). 4. Threadgold and Johnson (1999). 5. G. Rocamora in litt. (2008).

Text account compilers Andrew O'Brien (BirdLife International), John Pilgrim (BirdLife International), Pete Robertson (BirdLife International), Joe Taylor (BirdLife International)

Contributors Gerard Rocamora (Island Conservation Society/MNHN Paris Museum), A. Skerrett (Island Conservation Society)

IUCN Red List evaluators Stuart Butchart (BirdLife International), Joe Taylor (BirdLife International)

Recommended citation BirdLife International (2009) Species factsheet: Dicrurus aldabranus. Downloaded from http://www.birdlife.org on 10/2/2010

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

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