Justification This species is listed as Endangered because it has a very small range which is in decline. There has been a continuing reduction in the extent and quality of habitat. Despite this, the population does not appear to be declining.

Family/Sub-family Dicruridae

Species name author Schlegel, 1866

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

Identification 28 cm. Large, black bird with very long, deeply forked tail. Black plumage with deep greenish blue gloss. Tail fork shows the extremities splayed out, imparting a suggestion of a lyre shape. Bill black, strong; heavier and longer than those of D. adsimilis and D. macrocercus. Feet black. Iris red. Sexes alike, with males tending to be slightly larger. Juvenile brownish-black with less gloss, slightly paler underparts and not so well-developed tail fork. Voice Soft plitt plitt when hawking insects. Buzzing notes and scratchy cries including a loud tyok repeated several times, squaa-aa-kuchuk and throaty choo-kroo-kreech when alarmed at the nest. Song is a harsh jumble of chirps and squeaks. Pairs perform duets in their territories throughout the breeding season. Imitates call of other bird species.

Population estimate

Population trend

Range estimate (breeding/resident)

Country endemic?

5,000

stable

320 km²

Yes

Range & population Dicrurus waldenii occurs sparsely and locally on Mayotte (to France) in the Comoro island group. It is fairly widespread in the humid northern and western parts of the island, but may have a restricted ability to disperse between patches. It is found commonly over 200 m around Mts Hachiroungou, Mtsapéré, Combani and Bénara, Sohoa Forest, and at lower altitude along the west coast¹⁰. It is also found at lower densities in areas of degraded habitats between the four mountains, and in mangroves at Dzoumonyé-Bouyouni, Miréréni-Chirongui and Tsingoni-Mroale-Soulou¹⁰. It is absent from the entire southern peninsula, Mt Choungui and the lowland dry forests of Dapani-Sazilé¹⁰. Research up to 1994 showed it to be more abundant than Grand Comoro Drongo D. fuscipennis, with a population of at least 100 individuals^3,4,8. However, point counts and surveys of density conducted in 2002-2004, indicate a minimum population size of 2,500 pairs¹⁰.

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

Ecology: It occurs at the margins of evergreen forest¹, in secondary forest, thickets and plantations⁶, and also on the coast in mangroves and littoral woodland^3,5,7. It also occurs at low densities in areas with forest patches alternating with Ylang-ylang plantations, orchards, forest clearings and agricultural fields¹⁰. Recent research suggests that the species prefers higher altitude, possibly wet, locations and is more abundant in larger forest patches, and those with a higher percentage cover of tall trees⁸. It is insectivorous, with cicadas making up almost half of the prey items taken, and may also take small vertebrates, although this is yet to be recorded¹⁰. Nesting has been observed between September and February. The nest is a solid round cup made of intertwined plant fibres built on a fork in a variety of tree species. It has a clutch-size of one to three eggs¹⁰. The incubation period is 19-21 days, followed by a fledging period of 17-25 days^9,10. Juveniles are dependent for one month after fledging and then remain with their parents until the start of the next breeding season¹⁰. Nest failure may be as high as 75% due to predation¹⁰.

Threats Deforestation for cultivation and timber is probably the greatest threat given that Mayotte's dense human population is growing steadily and the majority are involved in traditional food cultivation. The mangroves around Baie de Bouéni are threatened by heavy sediment loads from the deforested interior. Devastating cyclones seem to occur about every 10 years^2,5. The potential introduction of new nest predators is an important threat¹⁰.

Conservation measures underway A network of 17 Réserves Forestières covering 57 km² has been established. The most important of these for D. waldenii are probably Combani (3 km²), Majimbini (13 km²), Dzoumonyé (4 km²), Tchaourembo, Voundzé, and Hajangoua⁵.

Conservation measures proposed Continue field surveys to establish the population, range and status of the species. Monitor the population through regular surveys. Study the species's ecology. Investigate possible limiting factors. Draw up conservation plans. Develop an environmental education programme to alleviate inevitable increases in pressure on remaining native habitat, and use the species as a flagship symbol of the need to preserve forest¹⁰.

References 1. Benson (1960). 2. Louette et al. (1988). 3. Louette et al. (1993). 4. M. Louette in litt. (1999). 5. Safford (2001). 6. Safford and Evans (1992). 7. R. Safford in litt. (1999). 8. Stevens and Louette (1999). 9. M. Louette in litt. (2007). 10. G. Rocamora in litt. (2008).

Text account compilers Jonathan Ekstrom (BirdLife International), John Pilgrim (BirdLife International), Sue Shutes (BirdLife International), Ann Sutton, Joe Taylor (BirdLife International), Ben Warren (BirdLife International)

Contributors Michael Louette (Royal Museum for Central Africa), Gerard Rocamora (Island Conservation Society), Roger Safford (BirdLife International)

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

Recommended citation BirdLife International (2009) Species factsheet: Dicrurus waldenii. Downloaded from http://www.birdlife.org on 9/2/2010

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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