VU
Yellow-bearded Greenbul Criniger olivaceus



Justification

Justification of Red List category
This species is suspected to be experiencing moderately rapid declines in population size due to habitat loss and degradation. It is therefore classified as Vulnerable.

Population justification
The total population is conservatively suspected to number somewhere in the region of 100,000-499,999 individuals based on a population of c.120,000 pairs in Liberia alone (Gatter 1997). This roughly equates to 66,667 - 333,333 mature individuals, here rounded to 66,700 - 333,000 mature individuals.

Trend justification
The population is inferred to be in decline owing to ongoing habitat destruction and fragmentation. Global Forest Change data on tree cover loss indicate that, over ten years to 2019, approximately 6.5% of tree cover with 75% canopy cover was lost from within the species’s range (Global Forest Watch 2020). However, the species's habitat is also subject to commercial logging, which may not be detected by remote-sensed data, but which may change the structure of the habitat and have a negative impact on the species's population (B. Phalan in litt. 2020). Arcilla et al., (2015) reported a capture rate of 2.70 Yellow-bearded Greenbuls per 10,000 net-metre-hours in Ghana in 1993-1995, and this fell to zero in 2008-2010, following a period when logging activity increased. The species's population is therefore precautionarily suspected to have undergone a reduction of more than 30% over the past ten years, placed here in the band 30-49%. The threats to the species are ongoing, so this rate of decline is suspected to continue into the future.

Distribution and population

The species is known from several sites in southeast Guinea (L. Fishpool in litt. 2007, 2012, H. Rainey in litt. 2007), Sierra Leone (areas include Gola Forest where locally common, population 750-1,600 birds, Loma Forest [Atkinson et al. 1996] and the Kangari Hills [P. Robertson in litt. 1998]), Liberia (from the coast to the northern border at Nimba, population c.120,000 pairs [Gatter 1997]), with c. 54,000 pairs in Sapo National Park alone (Freeman et al. 2018). This species has also been observed in most mixed-species flocks in intact forests throughout Liberia (Freeman et al., 2018). Côte d'Ivoire (Taï National Park where frequently recorded during surveys in 2001-2002 [H. Rainey in litt. 2007], Yapo Forest where common [Demey and Fishpool 1994, H. Rainey in litt. 1999], Haute Dodo and Cavally Forest reserves where rarely observed [H. Rainey in litt. 2007], Mabi Forest [Waltert et al. 1999], Mopri and possibly in Mont Peko National Park [H. Rainey in litt. 2007]), and Ghana (restricted to the wetter section of the forest zone of the south-west, being fairly common in Ankasa and Cape Three Points, and local elsewhere [Holbech 2005, Dowsett-Lemaire and Dowsett 2014])

Ecology

The species is found in the midstorey of lowland primary forest. In Liberia, it is also known from mature secondary forest, forest-grassland mosaic and gallery forest and is found in the northern mountains up to 800 m (Gatter 1997). In Côte d'Ivoire, it is found in most primary forest in Taï National Park, but is more common in the evergreen forest of Yapo Forest, possibly owing to the greater prevalence of dense understorey and epiphytes (Gartshore et al. 1995). It is mainly insectivorous. In Ghana, it appears localised and requires closed canopy habitats (Dowsett-Lemaire and Dowsett 2009). It feeds mainly at mid-levels, occasionally lower, probing bark of branches and lianas, occasionally also foliage (Fishpool 2008, Dowsett-Lemaire and Dowsett 2014).

Threats

The largest remaining area of Upper Guinea forest (43%) is now found in Liberia. This forest experienced an intense pressure at the end of the civil war in 1996, due to a sharp increase in commercial logging activities (van der Mark 2000) and large scale oil-palm plantations (F. Dowsett-Lemaire in litt. 2016). Large scale deforestation (in 1990 estimated to be c.6% annually) took place in Côte d'Ivoire, between the mid-1970s and 1990s, and this included encroachment on protected areas (Chatelain et al. 1996). Forests on the Guinea and Côte d'Ivoire border, near Mt Nimba, have little effective protection and  were still experiencing clearance for agriculture and logging c.2007 (H. Rainey in litt. 2007). In Ghana it is threatened by deforestation and even selective logging as it can no longer be found in heavily-logged sections of some forest reserves where it occurred previously (Dowsett-Lemaire and Dowsett 2014) and in Ghana, it is only protected in Ankasa Wildlife Reserve and Kakum National Park (Dowsett-Lemaire and Dowsett 2014). The rate of forest loss in the Upper Guinea region appeared to decline slightly owing primarily to a decrease in the rate of deforestation in Côte d'Ivoire (H. Rainey in litt. 2007, R. Demey per F. Dowsett-Lemaire in litt. 2016). Across the Upper Guinea region, forest survives in fragmented patches (van der Mark 2000), which face pressure for logging, agriculture and mining (Deikumah et al. 2014, Freeman et al. 2018). This species may also be affected by the impacts of climate change which could lead to habitat shifting through decline in habitat quality from rising temperatures and disruption to precipitation cycles (Baker and Willis 2014, Carr et al. 2014).

Conservation actions

Conservation Actions Underway
Taï National Park and periphery (including Haute Dodo and Cavally Forest Reserves) in Côte d'Ivoire is the largest and best-preserved area of Upper Guinea forest, but management needs improvement (H. Rainey in litt. 2007). In Sierra Leone Gola Rainforest National Park was officially designated in 2010.

Conservation Actions Proposed
Improve management of Taï National Park and periphery (H. Rainey in litt. 2007). Carry out surveys in order to assess the species's population size, once the security situation is conducive. Monitor rates of forest clearance across the species's range. In Taï National Park, take measures to mitigate the effects of rapid land-use changes outside the park (Gartshore et al. 1995). In Taï National Park and Gola Forest, take action to limit forest clearance and incorporate local people in the development of effective management plan including development of land use regulations, alternative livelihoods, ecotourism and other activities which will limit encroachment into the park (H. Rainey in litt. 2007). Effectively motivate forest guards to carry out patrols (H. Rainey in litt. 2007).

Identification

20 cm. Medium-sized, drab greenbul. Dark olive relieved only by yellow throat. Faintly paler olive on belly and vent with a hardly discernible rusty wash on tail. Paler lores and blue eye-ring (hardly noticeable in the field). Similar spp. Could be confused with Western Bearded Greenbul C. barbatus but is smaller and has green, not greyish-brown, underparts, and less puffy throat. Voice Soft chuk given whilst foraging and three harsh notes whut chruw chruw. Hints Usually occurs in groups of between two and, rarely, five birds in mixed-species flocks and has distinctive habit of foraging on vertical trunks and branches.

Acknowledgements

Text account compilers
Clark, J.

Contributors
Demey, R., Dowsett, R.J., Dowsett-Lemaire, F., Ekstrom, J., Fishpool, L., Freeman, B., Phalan, B., Rainey, H., Robertson, P., Shutes, S., Starkey, M., Symes, A., Taylor, J., Thompson, H.S. & Westrip, J.R.S.


Recommended citation
BirdLife International (2024) Species factsheet: Criniger olivaceus. Downloaded from https://datazone.birdlife.org/species/factsheet/yellow-bearded-greenbul-criniger-olivaceus on 27/02/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from https://datazone.birdlife.org on 27/02/2024.