Little-known African bird: observations on Loango Slender-billed Weaver Ploceus subpersonatus in Congo-Brazzaville

by Pierre Bulens and R.J. Dowsett, from Bulletin of the African Bird Club, volume 8.1, March 2001.

Loango Slender-billed Weaver Ploceus subpersonatus has a very limited distribution, from Cabinda and the lower Congo river, in Congo-Kinshasa (ex-Zaïre), north throughout most of coastal Gabon [5]. Until recently it was known north only to the Port-Gentil area [7], but has since been found in the Akanda area, near libreville, by P Christy (and RJD pers. obs.). The map also shows (as an open circle) a possible sight record from Boma [1]. As the species is deemed globally threatened [2] and certainly of conservation concern, it is important to place on record further information from coastal Congo-Brazzaville (including the first known photograph), it being an addition to that country's avifauna [4].

Mist-netting by PB at Pointe lndienne (04°45'S 11°48'E) revealed the presence of this species on 5 December 1998, as well as during subsequent visits, on 19 December 1998 and 23 May 1999. P. subpersonatus was also mist-netted at Pointe Noire (04°48'S 11°51 'E) on various dates between 16 January and 14 March 1999. A total of 50 individuals was measured (16 adult males, 20 adult females and 14 juveniles).

The 14 juveniles measured were generally similar to females. None of those examined exhibited signs of breeding, but active wing moult was noted in several of the adults in February-May.
The first adequate description of the male and female plumages was published by Chapin [l], at a time when the species was known from just a handful of specimens. It is a medium-sized weaver, noticeably larger than Slender-billed Weaver Ploceus pelzelni with which it has been stated to form a superspecies (with the extralimital P.luteolus) [5]. This appears doubtful: the two are not very alike and are largely sympatric, as in the Feman Vaz area of Gabon [6].

Chapin [1] presented a key to separate males, which can now be amended:
Smaller, wing 54-66 mm, culmen to base 14-18.5 mm; little or no brownish wash on the bright yellow nape or chest - P. pelzelni.

Larger, wing 67-72 mm, culmen to base 18-22 mm; a distinct brownish wash over the yellow of nape and chest - P. subpersonatus.

Loango Slender-billed Weaver, Congo (Pierre Bulens)

Chapin [1] also gave measurements of 48-53 mm for the tail of male P. subpersonatus. He separated females from those of P. pelzelni by their larger size and duller plumage (deeper, duller olive on back and wings, much duller yellowish on face and underparts, with a distinct buff wash over most of the underparts).
Loango Slender-billed Weaver inhabits a wide range of secondary habitats, often near water, including palm savanna. In Congo it occurs in seasonal or permanent coastal swamp within 0-1 km of the beach. At Pointe Indienne it was noted as absent from one of the two sites (a seasonal swamp) in May, when the wetland dried up. Despite its small range, its habitat requirements appear less specialised than initially supposed. Although meritorious of further study, the species is unlikely to be seriously threatened (i.e. the category 'Vulnerable' [2] may not be justified).

Acknowledgements
We thank Françoise Dowsett-Lemaire for comments on a draft of this note.

References

1. Chapin, J.P. 1954. The birds of the Belgian Congo. Part 4. Bull. Amer. Mus. Nat. Hist. 75B: 1-846.
2. Collar, N.J., Crosby, M.J. and Stanersfield, A.J. 1994. Birds to Watch 2: the World list of threatened birds. Cambridge, UK: Birdlife International.
3. Collar, N.J. and Stuart, S.N. 1985. Threatened Birds of Africa and related islands. Cambridge, UK: International Council for Bird Preservation.
4. Dowsett, R.J. and Dowsett-Lemaire, F. 1993. A Con tribution to the Distribution and Taxonomy Afrotropical and Malagasy Birds. Tauraco Res. Report No.5. Liege: Tauraco Press.
5. Hall, B.P. and Moreau, R.E. 1970. An Atlas of Speciation in African Passerine Birds. London, UK: Brit. Mus. (Nat. Hist.).
6. Rand, A.L., Friedmann, H. and Traylor, M.A. 1959. Birds from Gabon and Moyen Congo. Fieldiana Zool. 41: 219-411.
7. Sargeant, D. 1993. Gabon. A birders guide to Gabon, West Africa. Privately published.