Justification of Red List Category
The species is likely declining as a result of ongoing habitat loss. However, accurately reflecting such declines and the extinction risk of the species is not possible given current evidence, and it could potentially fall into any of the categories between Least Concern and Critically Endangered. Therefore, it has been reassessed here as Data Deficient, and further research to obtain estimates of population size and trend are urgently needed.
The global population size has not been quantified, but the species is described as locally common (del Hoyo et al. 2006). Gatter (1997) estimated that Liberia could contain 60,000 pairs, but given the recent evidence of the loss of occupied habitat, and its disappearance from areas where it had been thought to be locally common, it is likely that the global population size is much smaller than this, or the previous estimates from Gatter (1997) had been too high. In effect the population size is essentially unknown.
The population is suspected to be declining owing to ongoing habitat destruction. Tracewski et al. (2016) estimated the rate of forest loss within the species's range at c.0.5% per year between 2000 and 2012, which would roughly equate to c.4.9% over 10 years. However, this included large areas where the species is not known to occur. Phalan et al. (2013) failed to locate the species at all during surveys of Grand Gedeh County, even when using playback, despite Gatter (1997) saying that there could be as many as 4 males per 200m at Zwedru. Therefore, while it is likely appropriate to consider this species to be in decline, it is not possible to quantify the rate of decline, and it could fall anywhere between a slow decline and potentially an extremely rapid one.
Bathmocercus cerviniventris has a fragmented range from Guinea (one record from Sérédou but locally common on the Ziama Massif [Bützler 1996]; also recorded from Pic de Fon and Mont Bero Forest Reserves [H. Rainey in litt. 2007]), Sierra Leone (the Nimini Hills, Kono district, also Sandaru, probably Kankordu, Mongeri, Bumbuna and the Kangari Hills [Okoni-Williams 2001, F. Dowsett-Lemaire in litt. 2016], but apparently highly local [P. Robertson in litt. 1998]), Liberia (from the coast to the northern highlands, and has been described as frequent on Mt Nimba, although it may now be described as local) (Gatter 1997, F. Dowsett-Lemaire in litt. 2016), Côte d'Ivoire (Mt Nimba and Sipilou in the west, Taï National Park where its preferred habitat is rare [Gartshore et al. 1995], Marahoué National Park [P. Christy per L. D. C. Fishpool verbally 1998], and Gagnoa and Lamto in the south), and Ghana (very few records (3 specimens, the last of which was in 1900), and possible extinct [Dowsett-Lemaire and Dowsett 2009, 2014]). In Côte d'Ivoire, future surveys may well locate the species in Mt Peko National Park and mountains east of Mt Nimba (H. Rainey in litt. 1999). In 1997, in Liberia, on the basis of survey density estimates, the population was calculated to be at least 60,000 pairs (Gatter 1997); however, throughout much of its range it would appear to have an extremely local distribution and this population estimate may in fact be too large, especially as Phalan et al. (2013) did not find the species in Grand Gedeh County, even when using playback, despite Gatter (1997) reporting potential densities of as many as 4 males per 200m at Zwedru.
It is found in dense secondary vegetation bordering small creeks and rivers in various forest types (primary and secondary forest, swamp forest, gallery forest, sub-montane forest) and, more rarely, lowland forest (Gartshore et al. 1995, Gatter 1997, Urban et al. 1997). On the Ziama Massif, Guinea, it occurs in humid, open sites near old clearings within mature forest (Bützler 1996). Given the uncertainty and paucity of records, it is possible that the species has special habitat requirements that could be disrupted by human activity (B. Phalan in litt. 2018), although further research would be required to identify this. It forages near the ground, always in pairs, on invertebrates (Bützler 1996, del Hoyo et al. 2006). A recently-fledged chick was observed in Sierra Leone during late June, suggesting laying in May (del Hoyo et al. 2006).
Due to its specific habitat requirements the species is probably not at high risk from lowland commercial logging activities. However, such logging will affect adjoining habitat and may cause disturbance, as well as potentially damaging catchment areas and affecting habitat through run-off (H. Rainey in litt. 2007). A significant threat is the mining of iron ore and other minerals, which is a direct danger for this species in Guinea and Liberia. At the site investigated at Mt Nimba, Liberia (by Ben Phalan and F. Dowsett-Lemaire), the species was threatened by iron mining (ArcelorMittal). In fact, the birds seen in 2011 were expected to disappear, as the whole site was being destroyed (Dowsett-Lemaire and Phalan 2013, F. Dowsett-Lemaire in litt. 2016, B. Phalan in litt. 2018). Settlement of one IBA where the species was known to occur (Marahoue National Park) may have impacted the species, but it is now thought to be recovering (W. Egnonkou in litt. 2018).
Conservation Actions Underway
No targeted conservation action is known for this species.
12-13 cm. Small, rufous, brown and black warbler. Black head and breast with chestnut belly and flanks. Brown upperparts, with darker wings and tail. Female drab brown with slightly paler throat. Voice Distinctive, three-note, piercing, insect-like whistle. Hints Creeps along forest floor, cocking tail.
Text account compilers
O'Brien, A., Symes, A., Taylor, J., Shutes, S., Westrip, J., Starkey, M.
Fishpool, L., Egnankou, W., Thompson, H.S., Dowsett, R.J., Phalan, B., Allport, G., Huettmann, F., Dowsett-Lemaire, F., Rainey, H., Robertson, P.
BirdLife International (2020) Species factsheet: Bathmocercus cerviniventris. Downloaded from http://www.birdlife.org on 16/02/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 16/02/2020.