NT
Dja River Swamp-warbler Bradypterus grandis



Justification

Justification of Red List Category
This species is listed as Near Threatened because it is precautionarily suspected to have a moderately small population, but it is not thought to be declining. Its specialised marsh habitat is probably not threatened at the present time and the species is probably well distributed throughout much of its range in northern Gabon and southern Cameroon. It is known from eight widely separated locations and the paucity of records appears to be more likely owing to the inaccessibility of its marsh habitat and previously poor knowledge of its call.

Population justification
Fontaine (2003) suggests its population is 'not more than a few thousand individuals', and so it is tentatively placed in the band 1,000-2,499 individuals here. This is equivalent to 667-1,666 mature individuals, rounded here to 600-1,700 mature individuals.

Trend justification
The population is suspected to be in decline owing to ongoing habitat destruction.

Distribution and population

Bradypterus grandis is known from a total of nine localities in south-eastern Cameroon, Central African Republic (where it has been discovered in Dzangha-Ndoki National Park in the extreme south [P. Christy per F. Dowsett-Lemaire in litt. 2000, F. Dowset-Lemaire in litt. 2016]), and Gabon. It was previously thought rare and restricted but since its vocalisations have become known it has been recorded with greater frequency; in addition its preferred swamp habitat does not appear rare, but rather inaccessible and little visited. In Cameroon, one pair was recorded in the Nki Reserve (Dowsett-Lemaire and Dowsett 2000a), nine territories were identified in Lobéké National Park (Dowsett-Lemaire and Dowsett 2000a) where a population of at least 100 pairs is estimated (Dowsett-Lemaire and Dowsett 2000a), and it has been found at Bitye (del Hoyo et al. 2006). It was also found in March 2016 at a salt marsh along the Dja River in Ngoyla-Minton forest block (Borrow and Demey 2016). In Gabon, it is known from, Mimongo and M'Bigou in the Massif du Chaillu (Urban et al. 1997), from the Lopé National Park and most recently from Langhoué where at least eight singing birds were recorded (Fontaine 2003). It was previously thought rare in Gabon, but is now thought to be more common and widespread in the north of Gabon as suitable habitat there is extensive (P. Christy in litt. 1994, 1999, F. Dowsett-Lemaire in litt. 2000, Fontaine 2003). There are reportedly hundreds of suitable areas of Rhynchospora swamp in the forests of south-east Cameroon, eastern Gabon, northern Congo, and southern Central African Republic, but most are not easily accessible, and this is likely to explain the paucity of records (Fontaine 2003).

Ecology

It is found at 400-800 m and was thought to be a bird of contact zones between forest and open areas such as savannas and river borders, also occurring in tall elephant grass Pennisetum (Urban et al. 1997). However, recent research indicates that it is only found in dense sedges of Rhynchospora corymbosa, thus restricting it to small, isolated swamps in the forest zone (Dowsett-Lemaire and Dowsett 2000a). Its feeding and breeding ecology are unknown (Urban et al. 1997).

Threats

The species is potentially threatened by forest clearance accompanied by the drainage of adjacent swamps (Urban et al. 1997). However, this is not believed to be a threat at present.

Conservation actions

Conservation Actions Underway
Its habitat is protected in Lopé National Park and Dzanga-Ndoki National Park (del Hoyo et al. 2006). Nki may be likely to receive national park status (Dowsett-Lemaire and Dowsett 2000a) and Lobéké Reserve has been recognised as a National Park (F. Dowsett-Lemaire in litt. 2016).

Conservation Actions Proposed
Conduct further surveys to determine the extent of suitable Rhynchospora habitat within its probable range and estimate its population densities. Monitor population trends through regular surveys. Monitor potential threats to its habitat. Increase the area of suitable habitat that has protected status. Carry out research into the species's ecology and behaviour.

Identification

19 cm. Large warbler with long and broad tail. Overall deep brown with slightly russet tones on tail, mottled grey and brown throat and upper breast. Voice Slow chiddup chiddup which speeds up into staccato call, very often given in display flight and accompanied with whirring of wings.

Acknowledgements

Text account compilers
Ekstrom, J., Shutes, S., Symes, A., Taylor, J., Westrip, J.

Contributors
Sargeant, D., Christy, P., Dowsett, R.J., Dowsett-Lemaire, F.


Recommended citation
BirdLife International (2019) Species factsheet: Bradypterus grandis. Downloaded from http://www.birdlife.org on 24/08/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 24/08/2019.