Data Zone
Justification of Red List category
This species has a small range, with recent records from only seven locations. Significant areas of habitat remain, but it is likely to be declining rapidly in response to agricultural conversion, especially for shade coffee plantations. It is therefore listed as Endangered. However, if future studies reveal that it is able to survive in degraded habitats, it may qualify for downlisting to Vulnerable.
Population justification
The population is estimated to number 2,500-9,999 individuals based on an assessment of known records, descriptions of abundance and range size. This is consistent with recorded population density estimates for congeners or close relatives with a similar body size, and the fact that only a proportion of the estimated Extent of Occurrence is likely to be occupied. This estimate is equivalent to 1,667-6,666 mature individuals, rounded here to 1,500-7,000 mature individuals.
Trend justification
Although the species can still be found in patches of suitable habitat, ecosystem conversion and degradation are continuing unabated within the region, suggesting that populations are likely to be in decline, perhaps at a rate of 10-19% over ten years. Although it can occasionally be found in degraded forest, secondary forest and areas that have been previously cleared, it shows a strong preference for undisturbed humid forest with an intact understorey and is unlikely to persist successfully in the absence of primary forest (Sharpe 2008, C. J. Sharpe in litt. 2011).
Basileuterus griseiceps occupies a restricted range in north-east Venezuela in the Turimiquire Massif (both in the Serranía de Turimiquire the west of the San Antonio valley and the Cordillera de Caripe to the east) on the borders of Sucre, Anzoategui and Monagas. Since the 1960s, it has been recorded from nine localities: Buenos Aires, Cerro El Guamal, Cerro Tristeza, Cerro Turimiquire and Quiriquire (Piedra 'e Mole') in the Serranía de Turimiquire, and Macanillal, Cerro Negro, Cumbres de San Bonifacio and Cerro Gobierno in the Cordillera de Caripe (Colvee 1999, Azpúrua 2007, C. J. Sharpe in litt. 2011, 2015, Azpúrua et al. 2013, Sharpe 2015). Of these, it appears to be most numerous at Cerro Quiriquire (Piedra 'e Mole') (Azpúrua 2007, C. J. Sharpe in litt. 2011). On Cerro Negro, no more than ten small patches of suitable habitat remain (Boesman and Curson 1995, T. Brooks in litt. 1999). One patch was only 2 km2 and probably held 2-5 pairs (Boesman and Curson 1995). In 1993, one individual was observed on Cumbres de San Bonifacio (Boesman and Curson 1995).
It inhabits dense understorey in the interior or edge of undisturbed subtropical forest and natural clearings (Boesman and Curson 1995). It apparently survives in disturbed forest if there is a dense understorey (of e.g. Heliconia) (Boesman and Curson 1995), and is thought to be fairly generalist in habitat requirements (Anon. 2007). However, a recent survey found that abundance was higher in less fragmented forest (Anon. 2007). The majority of specimens have been taken at 1,400-2,100 m, but it has been recorded up to 2,580 m, and as low as 1,200 m (Boesman and Curson 1995, Colvee 1999, Azpúrua et al. 2013, Curson and Sharpe 2015). Breeding seems to occur from May to July, with juveniles fledging in August (Boesman and Curson 1995, Curson and Sharpe 2015). The only known nest was found in May in secondary vegetation around an old treefall gap (Hernández et al. 2009).
The entire Turumiquire Massif is under severe human pressure, which, through widespread clearance for agriculture and pasture, has resulted in extensive degradation of its montane forests. Even in El Guácharo National Park (incorporating Cerro Negro), there is forest clearance, burning and removal of the understorey for coffee (Boesman and Curson 1995). The slopes of Cerro Negro are largely bare, with the more obvious forest patches actually shade-coffee plantations (Boesman and Curson 1995). Shade-coffee cultivation safeguards some trees but destroys the understorey upon which this bird depends (Boesman and Curson 1995). There is conversion to coffee, mango, banana, and citrus plantations in the Serranía de Turumiquire, but extensive forested areas remain (Colvee 1999, C. J. Sharpe in litt. 2011). However, on Cumbres de San Bonifacio there are only two peaks above 1,400 m (Boesman and Curson 1995).
Conservation Actions Underway
Large areas of habitat persist within El Guácharo National Park, and the reserve has been expanded to include a further 500 km2 of largely undisturbed forest (Gabaldón 1992), although much of this is too low for this species (J. Pérez-Emán in litt. 2012). A programme of research into basic ecology has been carried out at the Central University of Venezuela (C. J. Sharpe in litt. 2011), resulting in much-needed information on the species' conservation status (Azpúrua 2007, Hernández et al. 2009, Azpúrua et al. 2013). It is considered nationally Endangered in Venezuela (Sharpe 2008, 2015).
14 cm. Green-and-yellow warbler with grey head. Deep olive-green upperparts. Bright yellow underparts. Grey head, lightly streaked black on crown with distinctive white supraloral spot and white speckling on ear-coverts. Similar spp. Sympatric Basileuterus warblers have striped heads that do not contrast with upperparts. Voice Thin tseck and harsh thack or chack calls. Hints Often with mixed-species flocks.
Text account compilers
Gilroy, J., Pople, R., Sharpe, C J
Contributors
Pérez-Emán, J., Sharpe, C J, Brooks, T.
Recommended citation
BirdLife International (2024) Species factsheet: Grey-headed Warbler Basileuterus griseiceps. Downloaded from
https://datazone.birdlife.org/species/factsheet/grey-headed-warbler-basileuterus-griseiceps on 22/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 22/11/2024.