Little Rush Warbler Bradypterus baboecala Scientific name definitions

This brownish warbler is widespread but patchily distributed through sub-Saharan Africa from Ethiopia south to South Africa and west to Angola. Extremely similar to Highland Rush Warbler (Bradypterus centralis), the two were considered conspecific until recent genetic data suggested they are each more closely related to other species (1 Alström, P., A. Cibois, M. Irestedt, D. Zuccon, M. Gelang, J. Fjeldså, M. J. Andersen, R. G. Moyle, E. Pasquet, and U. Olsson (2018). Comprehensive molecular phylogeny of the grassbirds and allies (Locustellidae) reveals extensive non-monophyly of traditional genera, and a proposal for new classification. Molecular Phylogenetics and Evolution 127:367–375. Close ); the two differ mostly in voice. Like many of its closest relatives, Little Rush Warbler uses marshes with reeds, sedges, and grasses along the edges of lakes, swamps, and around dams. Relatively little is known about their natural history, but they build their cup nest in a dense tussock of grass or rush, and both parents tend to the chicks. Their conservation status has not been assessed since Highland Rush Warbler was split from it, but it likely does not face any immediate conservation concerns.

A medium-sized warbler with short wings, well-graduated tail of 12 rounded feathers, slim bill, and dark throat streaks. Sexes alike. Juvenile has richer brown upperparts, yellowish wash below, narrower breast streaking. Subspecies variation is not pronounced.

Forms a group of swamp-dwelling species together with Dja River Swamp Warbler (Bradypterus grandis), Grauer's Swamp Warbler (B. graueri), and White-winged Swamp Warbler (B. carpalis). Until recently considered conspecific with Highland Rush Warbler (B. centralis), and vocal evidence points to their being separate species (a markedly higher frequency [score 3] and buzzier tone [2] in song (2 Boesman, P. (2016). Notes on the vocalizations of Little Rush-warbler (Bradypterus baboecala). HBW Alive Ornithological Note 237. In: Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. Close ), scores in brackets based on 3 Tobias, J. A., N. Seddon, C. N. Spottiswoode, J. D. Pilgrim, L. D. C. Fishpool, and N. J. Collar (2010). Quantitative criteria for species delimitation. Ibis 152(4):724–746. Close ); while genetic and vocal sampling is still incomplete, available genetic data does show that B. centralis is genetically distinct, and appears to be sister to B. graueri (4 Alström, P., S. Fregin, J. A. Norman, P. G. P. Ericson, L. Christidis, and U. Olsson (2011). Multilocus analysis of a taxonomically densely sampled dataset reveal extensive non-monophyly in the avian family Locustellidae. Molecular Phylogenetics and Evolution 58(3):513–526. Close , 1 Alström, P., A. Cibois, M. Irestedt, D. Zuccon, M. Gelang, J. Fjeldså, M. J. Andersen, R. G. Moyle, E. Pasquet, and U. Olsson (2018). Comprehensive molecular phylogeny of the grassbirds and allies (Locustellidae) reveals extensive non-monophyly of traditional genera, and a proposal for new classification. Molecular Phylogenetics and Evolution 127:367–375. Close ), while present species might be sister to the entire group (1 Alström, P., A. Cibois, M. Irestedt, D. Zuccon, M. Gelang, J. Fjeldså, M. J. Andersen, R. G. Moyle, E. Pasquet, and U. Olsson (2018). Comprehensive molecular phylogeny of the grassbirds and allies (Locustellidae) reveals extensive non-monophyly of traditional genera, and a proposal for new classification. Molecular Phylogenetics and Evolution 127:367–375. Close ). Distinctive song known from nominate B. baboecala and B. centralis elgonensis (5 Zimmerman, D. A., D. A. Turner, and D. J. Pearson (1996). Birds of Kenya and Northern Tanzania. Christopher Helm, London, United Kingdom. Close ), but genetic sampling of supposed nominate was from Nigeria; for geographical reasons, therefore, unsampled subspecies chadensis tentatively assigned here to present species, although recently discovered population in Ghana considered to refer to or be allied with B. baboecala msiri (6 Dowsett-Lemaire, F., and R. J. Dowsett (2014). The Birds of Ghana: An Atlas and Handbook. Tauraco Press, Liège, Belgium. Close ). Patchwork distribution of the two species further evident when B. baboecala abyssinicus was confirmed to sing like southern B. baboecala (7 Dowsett, R. J., and F. Dowsett-Lemaire (2015). New avian observations from south-western Ethiopia, with a review of overlooked literature and altitudinal limits. Bulletin of the British Ornithologists’ Club 135(3):224–239. Close ). Song of present species may be a character displacement produced by co-occurrence with B. carpalis, which sings like B. baboecala (8 Kennerley, P., and D. Pearson (2010). Reed and Bush Warblers. Christopher Helm, London, UK. Close ), suggesting a regional adaptation rather than a specific character; but molecular evidence counters this notion. Much more research needed.

Seven subspecies recognized.

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SUBSPECIES

Bradypterus baboecala chadensis Scientific name definitions

Distribution

L Chad.

Identification Summary

More rufous-brown above and larger than B. b. chadensis (wing 58 mm, versus 54–57 mm), sides and posterior underparts browner, and lacks throat streaks.

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SUBSPECIES

Bradypterus baboecala abyssinicus Scientific name definitions

Distribution

Ethiopia.

Identification Summary

Paler, warmer brown, above, tinged more tawny below, throat well streaked, and is most like race sudanensis.

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SUBSPECIES

Bradypterus baboecala tongensis Scientific name definitions

Distribution

SE Kenya, E and S Tanzania, E and S Zambia, Malawi, E Zimbabwe and NW, C and S Mozambique S to NE South Africa (E Northern Province, lowland KwaZulu-Natal) and E Swaziland.

Identification Summary

Has tawny-brown wash to breast, and tawny-brown flanks and undertail coverts. B. b. tongensis is warmer above than nominate, buffier below, with fainter throat streaks.

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SUBSPECIES

Bradypterus baboecala benguellensis Scientific name definitions

Distribution

W Angolan Plateau.

Identification Summary

Resembles transvaalensis, but larger (58–65 mm, versus 54–61 mm) and darker.

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SUBSPECIES

Bradypterus baboecala msiri Scientific name definitions

Distribution

SE DRCongo and N and W Zambia (to bordering SW Tanzania) S to E and SE Angola, extreme NE Namibia (Caprivi Strip) and NW Botswana.

Identification Summary

Darker (less rufescent) above, as well as on flanks and undertail coverts, and whiter below than nominate (more like transvaalensis), throat streaks pronounced and usually extend to upper breast and flanks.

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SUBSPECIES

Bradypterus baboecala transvaalensis Scientific name definitions

Distribution

C and SE Zimbabwe, N and E South Africa (highveld of Northern Province, W KwaZulu-Natal, Free State, E Griqualand), W Swaziland and lowlands of Lesotho.

Identification Summary

11·2–15 g. <em>B. b. transvaalensis</em> is whiter below than nominate, less olive-brown on flanks and undertail-coverts, but upperparts as nominate.

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SUBSPECIES

Bradypterus baboecala baboecala Scientific name definitions

Distribution

S South Africa (Western Cape, Eastern Cape).

Identification Summary

11·2–17 g. Nominate has top and side of head dark olive-brown, poorly marked buffish supercilium; upperparts warm dark brown, more rufous on rump; wings dark brown, pale scaly fringes on smaller wing-coverts; tail dark brown; grey-buff below, whiter on chin, throat and centre of belly, with dark brown streaks on lower throat; browner on breast-sides and flanks, more tawny-brown on undertail-coverts; iris brown; bill blackish above, greyish base below; legs pinkish brown. Sexes alike. Juvenile has richer brown upperparts, yellowish wash below, narrower and more defined breast streaking.

Little Rush Warbler has a patchy distribution across sub-Saharan Africa, ranging from southern South Africa north through Zimbabwe, Zambia, southeastern Democratic Republic of the Congo, Mozambique, Malawi, eastern and southern Tanzania, and southeastern Kenya. It ranges west in southern Africa to northeastern Namibia, northeastern Botswana, southern, eastern, and central Angola to the western Angolan Plateau. Two disjunct populations occur, one in Ethiopia and one around Lake Chad.

Some information presented here may refer to Highland Rush Warbler (Bradypterus centralis), but is presumably similar in present species. In northern and eastern Africa, mainly sedges and papyrus around lakes, dams, and highland swamps. Readily exploits suitable man-made habitats, although it has been suggested that such areas are only occupied temporally (see Movements). Sea-level, to 2,300 m in Kenya. Reeds and swamp vegetation by permanent water. In southern parts of range, sedges (Cyperus, Carex), reeds, and reedmace (Typha) around lagoons, estuaries, and sewage ponds, or along rivers and streams; in East Africa, mainly sedges and papyrus around lakes, dams and highland swamps. Sea-level to 2,120 m (Ethiopia) or 1,800 m (Zambia), with single record (of a territorial pair) at 2,300 m in Malawi.

Some information presented here may refer to Highland Rush Warbler (Bradypterus centralis), but is presumably similar in present species. Mainly sedentary, but an influx was recorded at Lake Baringo in February–April, and records at man-made wetlands in Kenya have been ascribed to wandering, rather than territorial, birds. Some local but quite extensive movements in Zimbabwe during winter months, and in South Africa in response to seasonal water-level changes, while single record on Nyika Plateau (Malawi, see Habitat), in December–January, also suggests occasional wandering.

Very little information. Some information presented here may refer to Highland Rush Warbler (Bradypterus centralis), but is presumably similar in present species. Small insects; ant eggs. Forages low down in vegetation, often over water; sometimes takes food on ground.

Vocal development

No information.

Vocal Array

Song. A series of identical short notes initially uttered at a hesitant steady pace, after a while speeding up and then ceasing abruptly, suggesting the rhythm of a bouncing ball: trip...trip...trip...trip...trip..trip..trip.trip.triptriptriptriptrip. Total number of notes and duration of a full song phrase is highly variable, typically has some 20 notes in 8s with an initial pace of about 1note/s and an end pace of 3‒6notes/s. The repeated note is also quite variable, but mostly sounds like a disyllabic chirp such as treep, tirrup, trup etc. with most energy between 1.5 and 3.5kHz and a duration of ⁓0.12‒0.16s. Often, towards the accelerating end of the song phrase a short flight display is performed, generating a rattling wing noise as the bird flutters and hovers with tail pointed downwards (9 Urban, E. K., C. H. Fry, and S. Keith, Editors (1997). The Birds of Africa. Volume 5. Thrushes to Puffback Flycatchers. Academic Press, London, UK. Close ). The rattle may be a continuous low-pitched trrrrrrrr of about 1s, or alternatively a series of pulses trrr...trrrr..trrrr. Song phrases are typically repeated many times, with only a few seconds interval.

Peenh. A single plaintive, nasal note peenh, repeated at irregular intervals. Note has a duration of ⁓0.25‒0.40s, fundamental frequency around 2kHz (but presumably polyphonic), and is either mildly overslurred or downslurred.

Other. Single chirps as in song may also be given occasionally. A sad bleating pee-et attributed to female has also been described (9 Urban, E. K., C. H. Fry, and S. Keith, Editors (1997). The Birds of Africa. Volume 5. Thrushes to Puffback Flycatchers. Academic Press, London, UK. Close ).

Geographic variation

Present species previously included Highland Rush Warbler B. centralis, and vocal difference (a.o. a distinct higher pitch of the latter) has been known since long (5 Zimmerman, D. A., D. A. Turner, and D. J. Pearson (1996). Birds of Kenya and Northern Tanzania. Christopher Helm, London, United Kingdom. Close ,10 Chappuis, C. (2000). Oiseaux d’Afrique 2. Afrique Occidentale et Centrale. 15 CD. Société d’Études Ornithologiques de France, Paris. Close ,8 Kennerley, P., and D. Pearson (2010). Reed and Bush Warblers. Christopher Helm, London, UK. Close ). Exact boundaries between both species (based on voice) have only recently become clearer, with a few remote disjunct populations still to be documented. High-pitched voice of Highland Rush Warbler is apparently confined to the highland region around lake Victoria, while all other populations have the low-pitched song of present species (11 Dowsett, R. J. (2015). Comments on the ornithology of Nigeria, including amendments to the national list. Bulletin of the British Ornithologists’ Club 135(2):154–173. Close ,2 Boesman, P. (2016). Notes on the vocalizations of Little Rush-warbler (Bradypterus baboecala). HBW Alive Ornithological Note 237. In: Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. Close ). This does not entirely match genetic findings (a Nigerian specimen part of B. centralis 4 Alström, P., S. Fregin, J. A. Norman, P. G. P. Ericson, L. Christidis, and U. Olsson (2011). Multilocus analysis of a taxonomically densely sampled dataset reveal extensive non-monophyly in the avian family Locustellidae. Molecular Phylogenetics and Evolution 58(3):513–526. Close ), and a broader vocal and genetic sampling seems required to confirm present taxonomic treatment. Geographic variation in song of B. baboecala has not been studied in detail, and may be largely masked by individual variation (with repertoire size of any single individual unknown). Nasal Peenh call has mainly been documented in South Africa, a wider coverage is desirable.

Phenology

Song has been recorded in all months, but song activity is likely more intense during the breeding season, e.g. most recordings of song in South African are between September and January.

Daily Pattern of Vocalizing

Little Rush Warbler is quite a vocal species, and can be heard most of the day. Singing starts at dawn, and continues intermittently for most of the morning, with another activity rise in late afternoon.

Places of Vocalizing

Typically sings from within the reeds, usually perched on a sedge stem, and during its fluttering display flight it stays low just above the top of the reed bed.

Sex Differences

Little information. Song is attributed to male (9 Urban, E. K., C. H. Fry, and S. Keith, Editors (1997). The Birds of Africa. Volume 5. Thrushes to Puffback Flycatchers. Academic Press, London, UK. Close ).

Social Content and Presumed Functions of Vocalizations

Little information. Song has a territorial function, and birds are often countersinging, defending their relatively small territories.

Often, towards the accelerating end of the song phrase a short flight display is performed, generating a rattling wing noise as the bird flutters and hovers with tail pointed downwards (9 Urban, E. K., C. H. Fry, and S. Keith, Editors (1997). The Birds of Africa. Volume 5. Thrushes to Puffback Flycatchers. Academic Press, London, UK. Close ). The rattle may be a continuous low-pitched trrrrrrrr of about 1s, or alternatively a series of pulses trrr...trrrr..trrrr.

Some information presented here may refer to Highland Rush Warbler (Bradypterus centralis), but is presumably similar in present species. Egg-laying recorded in August–September in Ethiopia, and April–November in Democratic Republic of the Congo and East Africa; September–March in southern Africa, but August–January (peak September) in Cape region of southern South Africa and March–May in Malawi. Monogamous; territorial, but tends to nest in groups, although not truly colonial, as even in ideal habitat densities are no more 0.1 pair/ha. Nest a deep, tightly woven cup of dry reeds and grasses, lined with fine fibers and rootlets, built over water or wet ground, less than 1.2 m up, usually in tussock of sedges or rushes; external diameter 75 mm, external depth 76 mm, internal diameter 45–51 mm, internal depth 38–50 mm. Clutch 2–4 eggs, exceptionally perhaps just one (usually two), pinkish, white, greenish, or pale cream with small pink, red, and brown markings concentrated at larger end, size 18.5–20.4 mm × 13.5–13.9 mm; incubated 12–14 days and young fledge after another 12–13 days, being tended by both parents. Nests sometimes parasitized by Dideric Cuckoo (Chrysococcyx caprius).

Status has not been assessed since Highland Rush Warbler (Bradypterus centralis) was split from present species, but still likely to be relatively secure. Prior to split, not considered globally threatened (Least Concern). Relative abundance somewhat variable, ranging from locally common to rare. Distribution fragmented in northern tropics, e.g. sparsely distributed in Ethiopia. More widespread and locally common in wetlands of eastern, central and southern Africa, where appears to readily adapt to suitable man-made wetland habitats, so potentially resilient even in face of drainage of natural areas. Overall, subspecies chadensis is considered to be rare, and the nominate subspecies considered to be somewhat rare and patchily distributed in the northwest portion of its range, but distinctly more widespread and numerous in south and east.