Data Zone
Justification of Red List category
The population size has not been quantified, but it is plausible that the species numbers less than 10,000 mature individuals. It is thought to decline due to the loss and degradation of forested habitat within the range. Given that the species was found to occur at several scattered localities, it is possible that it consists of several small subpopulations, the largest of which may number close to 1,000 mature individuals. Therefore, the species is listed as Near Threatened.
Population justification
The global population size has not been quantified. It has been described as uncommon, although it may be more common than suggested by field observations owing to its secretive habits (del Hoyo et al. 2007). It is likely that the species numbers below 10,000 mature individuals and given the separation of suitable habitat the largest subpopulation may be as few as 1,000 mature individuals, assuming that this are separate subpopulations due to the likelihood that there is little regular interchange of individuals between the widely separate occupied areas.
Trend justification
There are no adequate data to quantify trends for this species, although it is suspected to be declining owing to habitat destruction (del Hoyo et al. 2007).
This species is found in southern Luzon in the Philippines. It occurs at more than ten localities, including Sorsogon and Camarines Sur (P. Hosner in litt. 2012). It is considered uncommon, although numbers may be higher than is suggested by field observations owing to its secretive habits. The population is suspected to be declining owing to habitat destruction (del Hoyo et al. 2007).
This species inhabits broadleaf evergreen forest, forest edge, secondary growth, and can be found in the vicinity of limestone rocks and outcrops and amongst moss-covered rocks and boulders. It has been suggested that habitat quality may not be important for this species and that it may actually prefer scrubby forest, especially where there is a high proportion of bamboo (R. Hutchinson in litt. 2012). It ranges from the lowlands to 1,000 m, presumably feeding upon many types of invertebrates by foraging in the leaf litter. Breeding occurs from February to August, laying a clutch of two eggs (del Hoyo et al. 2007).
Habitat loss within its range has been, and continues to be, extensive (del Hoyo et al. 2007), presumably driven primarily by agricultural expansion and timber extraction.
Conservation and Research Actions Underway
It is present in the Quezon and Mount Isarog National Parks (del Hoyo et al. 2007).
Conservation and Research Actions Proposed
Assess the population size and establish a monitoring programme to quantify trends. Establish its ability to persist in degraded habitats. Identify and assess threats. Ensure that the Quezon and Mount Isarog National Parks are effectively protected.
20-22 cm. Forehead greyish-olive, shading on crown to olive, all with faint dark scales. Mantle and upper back olive with faint narrow dark scales, becoming uniform brown on lower back, paler on rump, where white tips of feathers form semi-concealed bar, uppertail-coverts dark rufescent brown, tail dark brown. Flight-feathers broadly edged brown with bold white tips on outer two and indistinct tip on third. Lores and narrow supercilium to above eye white, cheek and ear-coverts grey, finely streaked white, submoustachial stripe white, narrow malar streak blackish. Chin to upper breast white, neck and breast sides and middle to lower breast grey. Bill blackish-brown. Voice. Song a very high-pitched, thin "tit'tsu-tsuuuu-tsiiiii".
Text account compilers
Calvert, R., Allinson, T, Taylor, J., Ashpole, J, Elliott, N.
Contributors
Allen, D., Gonzalez, J.C., Hosner, P. & Hutchinson, R.
Recommended citation
BirdLife International (2024) Species factsheet: Bicol Ground-warbler Robsonius sorsogonensis. Downloaded from
https://datazone.birdlife.org/species/factsheet/bicol-ground-warbler-robsonius-sorsogonensis 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.