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Bradypterus graueri 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Passeriformes Locustellidae

Scientific Name: Bradypterus graueri
Species Authority: Neumann, 1908
Common Name(s):
English Grauer's Swamp-warbler, Grauer's Rush-warbler, Grauer's Scrub-Warbler, Grauer's Swamp Warbler
French Fauvette de Grauer
Taxonomic Source(s): del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A., Fishpool, L.D.C., Boesman, P. and Kirwan, G.M. 2016. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 2: Passerines. Lynx Edicions and BirdLife International, Barcelona, Spain and Cambridge, UK.
Identification information: 16 cm. Medium-sized, skulking, drab warbler. Dark brown overall. Mottling on throat. Long, broad tail has slight russet tinge. Similar spp. White-winged Scrub-Warbler B. carpalis has white in wings and pale underparts. African Bush-Warbler B. baboecala is smaller and paler. However, these species rarely, if ever, share the same marshes. Voice Fast trill, preceded (and sometimes followed) by a few loud chup notes. Hints Very vocal, singing in full view on top of stems, sometimes in duet (Dowsett-Lemaire 1990), or during short display-flight accompanied by wing-whirring and fanned, lowered tail.

Assessment Information [top]

Red List Category & Criteria: Endangered B2ab(ii,iii,iv,v) ver 3.1
Year Published: 2016
Date Assessed: 2016-10-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): Butynski, T.M., Dowsett-Lemaire, F. & Plumptre, A.
Facilitator/Compiler(s): Benstead, P., Ekstrom, J., Evans, M., Shutes, S., Starkey, M., Taylor, J. & Westrip, J.
Justification:
Despite being locally common, this species has a very small and severely fragmented area of occupancy within its small overall range. Many sites are being converted to cultivation or pasture. Thus the species's area of occupancy is declining and, by inference, so is the number of mature individuals. It is therefore classified as Endangered.

Previously published Red List assessments:

Geographic Range [top]

Range Description:Bradypterus graueri is found in Rwanda, Burundi, eastern Democratic Republic of Congo (DRC) and south-western Uganda. In Rwanda, it occurs in Rugezi Swamp (Vande Weghe 1983) (probably the largest subpopulation), in the marshes between the Virunga volcanos (Vande Weghe 1983), and in Nyungwe (Rugege) Forest (Vande Weghe 1983, Dowsett-Lemaire 1990). In Burundi, in 1984, the national population was estimated at only c.10 pairs, however at least 30 singing birds were estimated from Mwokora, Kibira National Park, in 2011 (Anon. 2011). In the DRC, it is known from at least six locations west of Lakes Edward and Kivu (Chapin 1953, Friedmann and Williams 1968, T. Butynski in litt. 1999). In Uganda, it occurs in Echuya Forest Reserve (the 700 ha Muchuya swamp formerly thought to hold large numbers, but c.50 pairs estimated here by Ellison [2009]) and Bwindi-Impenetrable National Park (c.400 birds) (Davenport et al. 1996, T. Butynski in litt. 1999). The density at Kamiranzovu Swamp, Nyungwe, is about 13 birds per ha based on surveys of singing birds (A. Plumptre in litt. 2007). The swamp is c.25 km2, resulting in an estimate of 33,000 birds at this site alone (A. Plumptre in litt. 2007). The species's total area of occupancy is probably c.200-250 km2 (Arinaitwe 1996, Mwambu 1999).

Countries occurrence:
Native:
Burundi; Congo, The Democratic Republic of the; Rwanda; Uganda
Additional data:
Estimated area of occupancy (AOO) - km2:250Continuing decline in area of occupancy (AOO):Yes
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:53300
Continuing decline in extent of occurrence (EOO):UnknownExtreme fluctuations in extent of occurrence (EOO):No
Number of Locations:11-100Continuing decline in number of locations:Yes
Extreme fluctuations in the number of locations:NoLower elevation limit (metres):1950
Upper elevation limit (metres):2600
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:The density at Kamiranzovu Swamp, Nyungwe, is about 13 birds per ha based on surveys of singing birds; the swamp is c.25km2, resulting in an estimate of 33,000 birds at this site alone (A. Plumptre in litt. 2007). Therefore the total population is conservatively estimated to be somewhere in the range 20,000-49,000 individuals.

Trend Justification:  The population is suspected to be in decline owing to the drainage of marshes for agriculture and the cutting and burning of marsh vegetation. The likely rate of decline has not been estimated.
Current Population Trend:Decreasing
Additional data:
Continuing decline of mature individuals:Yes
Extreme fluctuations:NoPopulation severely fragmented:Yes
Continuing decline in subpopulations:Unknown
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:No

Habitat and Ecology [top]

Habitat and Ecology:It is found in a wide variety of montane marshes, usually dominated by grass or sedge (Chapin 1953, Vande Weghe 1983, Dowsett-Lemaire 1990, Mwambu 1999). It feeds on small beetles, caterpillars, spiders and small seeds (Urban et al. 1997). It is monogamous and territorial. In Uganda there was some evidence of breeding activity in February-May (Mwambu 1999) and it may breed in March in the eastern DRC (Chapin 1953). At least two nests have been found in Rwanda; one in Rugezi Swamp and the other in Kabatwa Swamp in the Volcanoes National Park (Anon. 2007). The latter was described as a small cup-shaped nest constructed from Poa leptocrada and other sedges, and perched in foliage 35 cm above the ground (C. Nsabagasani per Anon. 2007).

Systems:Terrestrial; Freshwater
Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):3.5
Movement patterns:Not a Migrant

Threats [top]

Major Threat(s): Rugezi Swamp was formerly unprotected and was being encroached by agriculture and progressively degraded by cutting and burning of vegetation during the dry season (Kanyamibwa 2001). However, it is now better protected as it supplies water to the hydroelectric dam at Lake Bulera, which provides power to Kilagi (A. Plumptre in litt. 2007). Following power cuts in 2005-2006, the government has moved people away from the swamp to ensure the protection of this water supply (A. Plumptre in litt. 2007). Marsh habitat in Nyungwe Forest was formerly threatened by gold-mining, but by 1989 this threat had disappeared (Dowsett-Lemaire 1990). In DRC, many parts of the range are densely settled and many montane marshes have been drained for cultivation or pasture (Sarmiento and Butynski 1997). In Burundi habitat at Mwokora is threatened by cutting for mats and thatching, and other valley swamps in Kibira National Park are threatened by encroaching agriculture (Anon. 2011). A climate change modelling exercise identified the species as one of the Albertine Rift endemics likely to be most severely affected by climate change (Anon. 2009).

Conservation Actions [top]

Conservation Actions: Conservation Actions Underway
In Uganda, Bwindi-Impenetrable National Park is well protected, and since 2004 the RSPB and NatureUganda have been working to conserve Echuya Forest Reserve (Arinaitwe 1996, T. Butynski in litt. 1999, Mwambu 1999, Anon. 2011). Work at Echuya has included development of a management plan, Collaborative Forest Management arrangements, planting of tree and bamboo seedlings to reduce pressure on the forest, income-generating activities to improve local livelihoods, environmental education, local empowerment, training and capacity-building, and watershed management (Anon. 2011). In Rwanda, reports suggest that Nyungwe Forest Reserve has suffered little encroachment recently, due to human emigration following conflict in the area (F. Dowsett-Lemaire in litt. 2000). In DRC, the only protected swamps are in Kahuzi-Biéga National Park and on Mt Tshiaberimu, and the former area is not secure (Hall et al. 1998). Since July 2006, a team have been monitoring the species in the Volcanoes National Park, Rwanda (Anon. 2007). An international and two national (Uganda and Rwanda) action plans have been developed for the species (Anon. 2009).

Conservation Actions Proposed
Conduct surveys to assess the species's total population size. Monitor the species's population across its range. Monitor habitat trends across the species's range. Ensure the continued protection of Rugezi Swamp in Rwanda (Hall et al. 1998). Continue to assess the current status of the main swamp areas in Nyungwe Forest. Confirm its absence from the Itombwe massif (T. Butynski in litt. 1999). Continue to search for nests and carry out research into its breeding biology in order to aid surveys and habitat management (P.K. Ndang'ang'a per Anon. 2007).

Classifications [top]

5. Wetlands (inland) -> 5.7. Wetlands (inland) - Permanent Freshwater Marshes/Pools (under 8ha)
suitability:Suitable season:resident major importance:Yes
5. Wetlands (inland) -> 5.5. Wetlands (inland) - Permanent Freshwater Lakes (over 8ha)
suitability:Suitable season:resident major importance:Yes
1. Land/water protection -> 1.1. Site/area protection

In-Place Research, Monitoring and Planning
  Action Recovery plan:Yes
  Systematic monitoring scheme:Yes
In-Place Land/Water Protection and Management
  Conservation sites identified:Yes, over entire range
  Occur in at least one PA:Yes
  Invasive species control or prevention:No
In-Place Species Management
  Successfully reintroduced or introduced beningly:No
  Subject to ex-situ conservation:No
In-Place Education
  Subject to recent education and awareness programmes:No
  Included in international legislation:No
  Subject to any international management/trade controls:No
11. Climate change & severe weather -> 11.1. Habitat shifting & alteration
♦ timing:Future ♦ scope:Whole (>90%) ♦ severity:Slow, Significant Declines ⇒ Impact score:Low Impact: 5 
→ Stresses
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

2. Agriculture & aquaculture -> 2.1. Annual & perennial non-timber crops -> 2.1.2. Small-holder farming
♦ timing:Ongoing ♦ scope:Majority (50-90%) ♦ severity:Slow, Significant Declines ⇒ Impact score:Medium Impact: 6 
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

2. Agriculture & aquaculture -> 2.3. Livestock farming & ranching -> 2.3.2. Small-holder grazing, ranching or farming
♦ timing:Ongoing ♦ scope:Majority (50-90%) ♦ severity:Slow, Significant Declines ⇒ Impact score:Medium Impact: 6 
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

3. Energy production & mining -> 3.2. Mining & quarrying
♦ timing:Past, Unlikely to Return ♦ scope:Minority (<50%) ♦ severity:Negligible declines ⇒ Impact score:Past Impact 
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

5. Biological resource use -> 5.2. Gathering terrestrial plants -> 5.2.2. Unintentional effects (species is not the target)
♦ timing:Ongoing ♦ scope:Minority (<50%) ♦ severity:Slow, Significant Declines ⇒ Impact score:Low Impact: 5 
→ Stresses
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

1. Research -> 1.2. Population size, distribution & trends
1. Research -> 1.3. Life history & ecology
3. Monitoring -> 3.1. Population trends
3. Monitoring -> 3.4. Habitat trends

Bibliography [top]

Anon. 2003. Spotted Ground Thrush threatened by forest destruction. Bird Numbers 12: 36.

Anon. 2007. Survey uncovers Grauer’s Swamp-warbler nest. Available at: #http://www.birdlife.org/news/news/2007/04/grauers_nest_discovery.html#.

Anon. 2009. Focus on a species. BirdLife Africa Newsletter 11(3): 38.

Anon. 2011. Conserving Echuya Forest, Uganda. Available at: http://www.rspb.org.uk/ourwork/projects/details/202034-conserving-echuya-forest-uganda.

Anon. 2011. Grauer’s Swamp Warbler mistnetted at Kibira National Park – Burundi. Available at: http://www.birdlife.org/community/2011/02/grauer%E2%80%99s-swamp-warbler-mistnetted-at-kibira-national-park-burundi/.

Arinaitwe, J. 1996. Grauer's Bush-warbler Bradypterus graueri. East African Natural History Society Bulletin 26: 14-15.

Chapin, J. P. 1953. Birds of the Belgian Congo. Bulletin of the American Museum of Natural History 75A, Part 3.

Collar, N. J.; Stuart, S. N. 1985. Threatened birds of Africa and related islands: the ICBP/IUCN Red Data Book. International Council for Bird Preservation, and International Union for Conservation of Nature and Natural Resources, Cambridge, U.K.

Davenport, T.; Howard, P.; Matthews, R. 1996. Echuya and Mafuga Forest Reserves.

Dowsett-Lemaire, F. 1990. Eco-ethology, distribution and status of Nyungwe Forest birds, Rwanda. In: Dowsett, R.J. (ed.), Enquête faunistique et floristique dans la Forêt de Nyungwe, Rwanda, pp. 31-85. Tauraco Press, Ely, U.K.

Ellison, M. 2009. A survey of Echuya Central Forest Reserve, Uganda, for the breeding population of Grauer's Swamp Warbler Bradypterus graueri. Scopus: 7-10.

Friedmann, H.; Williams, J. G. 1968. Notable records of rare or little-known birds from western Uganda. Revue de Zoologie et Botanique Africaine 77(1-2): 11-36.

Hall, J. S.; Saltonstall, K.; Inogwabini, B.-I.; Omari, I. 1998. Distribution, abundance and conservation status of Grauer's gorilla. Oryx 32: 122-130.

IUCN. 2016. The IUCN Red List of Threatened Species. Version 2016-3. Available at: www.iucnredlist.org. (Accessed: 07 December 2016).

Kanyamibwa, S. 2001. Rwanda. In: Fishpool, L.D.C.; Evans, M.I. (ed.), Important Bird Areas in Africa and associated islands: Priority sites for conservation, pp. 703-710. Pisces Publications and BirdLife International (BirdLife Conservation Series No.11), Newbury and Cambridge, UK.

Mwambu, P. 1999. Some aspects of the conservation biology of Grauer's Rush (Swamp) Warbler (Bradypterus graueri Neumann, 1908). Thesis. MSc (Zoology), Makerere University, Kampala, Uganda.

Sarmiento, E. E.; Butynski, T. M. 1997. Preliminary report on the Mt. Tshiaberimu survey.

Urban, E. K.; Fry, C. H.; Keith, S. 1997. The birds of Africa vol. V. Academic Press, London.

Vande weghe, J. P. 1983. Sympatric occurence of the White-winged Warbler Bradypterus carpalis and Grauer's Rush-warbler B. graueri in Rwanda. Scopus 7(3/4): 85-88.


Citation: BirdLife International. 2016. Bradypterus graueri. The IUCN Red List of Threatened Species 2016: e.T22714468A94417750. . Downloaded on 23 May 2017.
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