Dicrurus aldabranus

Taxonomy

Assessment Information

Geographic Range

Population

Habitat and Ecology

Threats

Conservation Actions

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Taxonomy [top]

Kingdom	Phylum	Class	Order	Family
ANIMALIA	CHORDATA	AVES	PASSERIFORMES	DICRURIDAE

Scientific Name:

Dicrurus aldabranus

Species Authority:

(Ridgway, 1893)

Common Name/s:

English	–	Aldabra Drongo
French	–	Drongo d'Aldabra

Assessment Information [top]

Red List Category & Criteria:

Near Threatened ver 3.1

Year Published:

2012

Assessor/s:

BirdLife International

Reviewer/s:

Butchart, S. & Taylor, J.

Contributor/s:

Rocamora, G. & Skerrett, A.

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.

History:

2008	–	Near Threatened
2004	–	Near Threatened
1988	–	Near Threatened

Geographic Range [top]

Range Description:	Dicrurus aldabranus is found on all four main islands of the Aldabra atoll and neighbouring islets, Seychelles (Penny 1974, G. Rocamora in litt. 2008), 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 (A. Skerrett in litt. 1999, G. Rocamora in litt. 2008). Its extent of occurrence is less than 150 km²(Stoddart and Westoll 1979). In 1983, the total population was estimated at c.1,500 individuals. It is widely distributed but generally uncommon (Stoddart and Westoll 1979).
Countries:	Native: Seychelles
Range Map:	Click here to open the map viewer and explore range.

Population [top]

Population:	In 1983, the total population was estimated to number c.1,500 individuals, equivalent to c.1,000 mature individuals.
Population Trend:	Stable

Habitat and Ecology [top]

Habitat and Ecology:	This species frequents mixed scrub, mangroves and Casuarina coastal forest (Penny 1974, Stoddart and Westoll 1979, Threadgold and Johnson 1999, G. Rocamora in litt. 2008), but prefers to breed in the latter two habitats, perhaps because the taller trees provide better nesting sites (G. Rocamora in litt. 2008). Territory size ranges from 2.25 ha in Casuarina woodland to 4.5 ha in mixed scrub (G. Rocamora in litt. 2008). 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 season (G. Rocamora in litt. 2008).
Systems:	Terrestrial

Habitat and Ecology:

This species frequents mixed scrub, mangroves and Casuarina coastal forest (Penny 1974, Stoddart and Westoll 1979, Threadgold and Johnson 1999, G. Rocamora in litt. 2008), but prefers to breed in the latter two habitats, perhaps because the taller trees provide better nesting sites (G. Rocamora in litt. 2008). Territory size ranges from 2.25 ha in Casuarina woodland to 4.5 ha in mixed scrub (G. Rocamora in litt. 2008). 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 season (G. Rocamora in litt. 2008).

Systems:

Terrestrial

Threats [top]

Major Threat(s):	It has a high rate of nest failure, probably largely due to introduced predators (G. Rocamora in litt. 2008). 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 experiments (G. Rocamora in litt. 2008). 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 cyclones (G. Rocamora in litt. 2008).

Major Threat(s):

It has a high rate of nest failure, probably largely due to introduced predators (G. Rocamora in litt. 2008). 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 experiments (G. Rocamora in litt. 2008). 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 cyclones (G. Rocamora in litt. 2008).

Conservation Actions [top]

Conservation Actions:	Conservation Actions Underway Aldabra is protected as a nature reserve under Seychelles legislation (G. Rocamora in litt. 2008). Conservation Actions Proposed Conduct surveys to obtain an up-to-date population estimate. Monitor population trends through regular surveys. Eradicate introduced predators (G. Rocamora in litt. 2008) and exclude native predators from nest-sites. Protect additional habitat on other islands and islets.

Conservation Actions:

Conservation Actions Underway
Aldabra is protected as a nature reserve under Seychelles legislation (G. Rocamora in litt. 2008).

Conservation Actions Proposed
Conduct surveys to obtain an up-to-date population estimate. Monitor population trends through regular surveys. Eradicate introduced predators (G. Rocamora in litt. 2008) and exclude native predators from nest-sites. Protect additional habitat on other islands and islets.

Citation:	BirdLife International 2012. Dicrurus aldabranus. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 21 May 2013.
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