Robsonius sorsogonensis 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Passeriformes Locustellidae

Scientific Name: Robsonius sorsogonensis (Rand & Rabor, 1967)
Common Name(s):
English Bicol Ground-warbler, Grey-banded Babbler
Taxonomic Source(s): del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A., Fishpool, L.D.C., Boesman, P. and Kirwan, G.M. 2016. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 2: Passerines. Lynx Edicions and BirdLife International, Barcelona, Spain and Cambridge, UK.
Identification information: 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".

Assessment Information [top]

Red List Category & Criteria: Near Threatened ver 3.1
Year Published: 2016
Date Assessed: 2016-10-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): Hosner, P., Gonzalez, J.C., Hutchinson, R. & Allen, D.
Facilitator/Compiler(s): Calvert, R., Taylor, J., Allinson, T & Ashpole, J
This species is listed as Near Threatened. It has a small range, within which it is found at a relatively limited number of locations and its habitat is declining both in area and quality as a result of deforestation; hence it almost meets the requirements for listing as threatened under criterion B1ab(ii,iii,v). If new data shows that it is found at fewer than 10 locations it would warrant uplisting to Vulnerable.

Previously published Red List assessments:

Geographic Range [top]

Range Description:This species is found in southern Luzon in the Philippines. P. Hosner in litt. (2012) gathered information on this species’s locality and reported that it is found at more than ten locations, including Sorsogon and Camarines Sur. 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).

Countries occurrence:
Additional data:
Continuing decline in area of occupancy (AOO):Yes
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:5228
Continuing decline in extent of occurrence (EOO):UnknownExtreme fluctuations in extent of occurrence (EOO):No
Number of Locations:11-15Continuing decline in number of locations:Unknown
Extreme fluctuations in the number of locations:No
Upper elevation limit (metres):1000
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population: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).

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).

Current Population Trend:Decreasing
Additional data:
Number of mature individuals:UnknownContinuing decline of mature individuals:Yes
Extreme fluctuations:NoPopulation severely fragmented:No
Continuing decline in subpopulations:Unknown
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:No

Habitat and Ecology [top]

Habitat and Ecology: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 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).

Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):5.5
Movement patterns:Not a Migrant

Threats [top]

Major Threat(s): 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 Actions [top]

Conservation Actions: 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 establish 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.

Citation: BirdLife International. 2016. Robsonius sorsogonensis. The IUCN Red List of Threatened Species 2016: e.T22735664A95116806. . Downloaded on 24 May 2018.
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