The Bicol ground warbler (Robsonius sorsogonensis) is a species of passerine bird in the family Locustellidae. It is native to southern Luzon and Catanduanes in the Philippines. It was formerly conspecific and forms a species complex with the Cordillera ground warbler and Sierra Madre ground warbler, which are some of most elusive birds in the country due to their extremely shy nature. Its natural habitat is tropical moist lowland forest. It is threatened by habitat loss.
| Bicol ground warbler | |
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Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Passeriformes |
| Family: | Locustellidae |
| Genus: | Robsonius |
| Species: | R. sorsogonensis
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| Binomial name | |
| Robsonius sorsogonensis | |
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| Synonyms | |
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Napothera sorsogonensis | |
Description and taxonomy
editEBird describes the bird as "A medium-sized bird of lowland and foothill forest floor, often in rocky areas. Fairly stout of body and bill, with long legs and large feet. Pale below with a grayish band across the chest and brown under the base of the tail. Note white throat, brown upperparts with two dotted white wingbars, rufous edging to the wing and tail feathers, and thin black moustache stripe. Unmistakable. Song consists of a very high-pitched “tseeeep soo tseeeep!"[2]
The three species of ground warblers are similar in size, shape and in the coloration of their juvenile plumage, but they differ from one another in their adult plumage coloration.It is differentiated from the Cordillera ground warbler and Sierra Madre ground warbler by its more brownish gray rathern than rusty brown plummage, a white throat and a gray breastband without scaling. [3]
The Bicol ground warbler was described by the ornithologists Austin L. Rand and Dioscoro S. Rabor in 1967 and given the binomial name Napothera sorsogonensis where it was conspecific with the Cordillera ground warbler and Sierra Madre ground warbler. The specific epithet is from the name of the province Sorsogon in the Bicol Region of the Philippines where the species was first discovered.[4] It was initially believed to belong to the Old World babblers family Timaliidae and given the English name "grey-banded babbler" but this was changed to "Bicol ground warbler" when its taxonomic position was better understood.[5][6] It is now placed in the genus Robsonius that was introduced by the English ornithologist Nigel J. Collar in 2006.[7]
Behaviour and ecology
editFood and feeding
editBased on the stomach contents of a collected specimen, the diet of the Bicol ground warbler is primarily invertebrates; it has been sighted scouring forest floors for prey hidden under leaves. While foraging it is known to cock its tail anywhere from 30 to 60 degrees.
Breeding
editVery little is known about its breeding habits. It breeds from February to August with a fledgling observed in late February. Nest is a large dome with a front entrance slightly above the ground. Clutch size is 2 white eggs with red speckles.[3]
Habitat and conservation status
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It is found in lowland moist dipterocarp forest in primary forest, secondary forest and forest edge up to 1,000 m. It is typically found among limestone outcrops, bamboo and mossy rocks.[8]
IUCN has assessed this bird as near threatened. The population size has not been quantified, but it is plausible that the species numbers less than 10,000 mature individuals. This species' main threat is habitat loss with wholesale clearance of forest habitats as a result of logging, agricultural conversion and mining activities occurring within the range.
It is found in two protected areas in Quezon Protected Landscape and Mount Isarog National Park; however, like most areas in the Philippines protection is lax.
Conservation actions proposed include assessing the population size and establishing a monitoring programme to quantify trends; establishing its ability to persist in degraded habitats; identifying and assessing threats; and ensuring that the Quezon Protected Landscape and Mount Isarog National Park are more effectively protected.
References
edit- ^ BirdLife International (2015). "Robsonius sorsogonensis". The IUCN Red List of Threatened Species (2015). doi:10.2305/IUCN.UK.2015-4.RLTS.T22735664A83679652.en.
- ^ "Bicol Ground Warbler". Ebird. Archived from the original on 2020-03-21.
- ^ a b Collar, Nigel; Robson, Craig; Sharpe, Christopher J. (2020). "Bicol Ground-Warbler (Robsonius sorsogonensis), version 1.0". Birds of the World. doi:10.2173/bow.gybbab2.01species_shared.bow.project_name. ISSN 2771-3105.
- ^ Rand, Austin L.; Rabor, Dioscoro S. (1967). "New birds from Luzon, Philippine Islands". Fieldiana Zoology. 51 (6): 85–89 [86].
- ^ Hosner, P.A.; Boggess, N.C.; Alviola, P.; Sánchez-González, L.A.; Oliveros, C.H.; Urriza, R.; Moyle, R.G. (2013). "Phylogeography of the Robsonius Ground-Warblers (Passeriformes: Locustellidae) reveals an undescribed species from northeastern Luzon, Philippines". Condor. 115 (3): 630–639. doi:10.1525/cond.2013.120124. hdl:1808/14475.
- ^ Gill, Frank; Donsker, David, eds. (2018). "Grassbirds, Donacobius, Malagasy warblers, cisticolas, allies". World Bird List Version 8.1. International Ornithologists' Union. Retrieved 12 May 2018.
- ^ Collar, N.J. (2006). "A partial revision of the Asian babblers (Timaliidae)" (PDF). Forktail. 22: 85–112 [108].
- ^ Allen, Desmond (2020). Birds of the Philippines. Barcelona: Lynx and Birdlife Guides International. pp. 274–277.
- Collar, N. J. & Robson, C. 2007. Family Timaliidae (Babblers) pp. 70 – 291 in; del Hoyo, J., Elliott, A. & Christie, D.A. eds. Handbook of the Birds of the World, Vol. 12. Picathartes to Tits and Chickadees. Lynx Edicions, Barcelona.