Cordillera ground warbler

Cordillera ground warbler
Conservation status
Vulnerable (IUCN 3.1)[1]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Passeriformes
Family:	Locustellidae
Genus:	Robsonius
Species:	R. rabori
Binomial name
Robsonius rabori Rand, 1960
Synonyms
Napothera rabori

The Cordillera ground warbler (Robsonius rabori), also known as Rabor's wren-babbler or the Luzon wren-babbler, is a species of bird currently placed in the family Locustellidae. It is endemic to the Philippines found in the Northwest Luzon in the foothills of the Cordillera Mountain Range. Some taxonomists continue to list the species in the Timaliidae, others in the Pellorneidae.There are no known photographs of live Cordillera ground warblers in the wild.

Its natural habitat is tropical moist lowland forests. It is threatened by habitat loss.

Description and Taxonomy[]

A side view of a stuffed specimen in the Naturalis Biodiversity Center

The Cordillera ground warbler has a length of 20–22 cm (7.9���8.7 in). It has rather notable long legs and a long bill and feet. Its feathers tipped dusky brown and it has a rusty-chestnut head with a thin whitish eye ring with a small area of bare gray skin behind the eye. Its throat is white and has black tips on the outside of it. The breast is a medium neutral gray with a distinct grayish triangular patter, with feather shafts slightly paler and a white belly. It also has chestnut wings to dark brown wings with each feather tucked in so it appears mostly chestnut when folded. It has brown upperparts with two dotted white wingbars The bird sings very high-pitched songs with the sound of “tseeee sip tseeee!” which often last between approximately 1.6 and 2.2 seconds.^[2][3]

It is differentiated from the Bicol ground warbler and Sierra Madre ground warbler with its grayish triangular markings on its belly. ^[3]

The Cordillera ground warbler was described by the Canadian zoologist Austin L. Rand in 1960 and given the binomial name Napothera rabori. The specific epithet

A bottom view of a stuffed specimen in the Naturalis Biodiversity Center

was chosen to honour Dioscoro S. Rabor who had collected the type specimen on the Philippine island of Luzon.^[4]

Ground warblers were first discovered in 1959 by an expedition team headed by Dioscoro S. Rabor. They conducted walking surveys of 2,000 meters each and recorded all of the bird calls they observed. There were initially two varieties discovered, now called the Cordillera ground warbler (Robsonius rabori) and the Bicol ground warbler (Robsonius sorsogonensis). The latter was first observed in 1961. The physical distinctions between them are mainly different coloration and geographic range. Originally, they had been classified as a member of the genus Nathopera because it was believed they were closely related to southeast Asian Napothera babblers. They were later lumped into the same species, but afterwards morphological evidence, behavioral observations, and the phylogeny of these birds led to their reclassification into a different genus, Robsonius, within the family Timaliidae. In 2013, a new species was discovered: the Sierra Madre ground warbler (Robsonius thompsoni). There are two other subspecies of the ground warbler: mesoluzonica and another from the Camarines Sur.

Behaviour and ecology[]

Breeding[]

Very little is known about the Cordillera ground warblers breeding method. The nest are mostly found on rock cliffs, made up of wet sticks, branches, and leaves. The nest is a dome shape and has an entrance way in it. The dome is held up by twigs attached to the rock and mud that surrounds it.

Food and feeding[]

The diet of the Cordillera ground warbler is primarily invertebrates, it has been sighted scouring forest floors for prey hidden under leaves.

Habitat and Conservation Status[]

The Cordillera ground warbler are found in the Luzon Island complex. They are found in the northwest Luzon in the Cordillera Mountain Range. It is found in lowland moist dipterocarp forest in primary forest, secondary forest and forest edge up to 500 m. It is typically found on the forest floor among limestone outcrops, bamboo and mossy rocks. ^[3]

IUCN has assessed this bird as vulnerable with the population being estimated at 2,500 to 9,999 mature individuals. Among the three Robsonius ground-warblers, the Cordilera ground-warbler is the most endangered owing to having the smallest range. 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.

This species is currently being protected within the Northern Sierra Madre Natural Park and Kalbario–Patapat Natural Park however like most areas in the Philippines protection is lax. Proposed efforts have been put forth to monitor the species further, and obtain information about how it can further be protected, however no other efforts are being used.

Conservation actions proposed include to 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 Northern Sierra Madre Natural Park and Kalbario–Patapat Natural Park are more effectively protected.

Description[]

EBird describes the bird as "A fairly small bird. Rufous-brown on the wings, back, and tail, with a gray head, heavily streaked pale underparts, and a black face and moustache stripe. Often found in mixed-species flocks. Somewhat similar to Stripe-headed rhabdornis and Grand rhabdornis, but smaller, with a white eye-ring rather than a black band through the eye. Voice includes a loud rattling trill and various quiet chips and squeals."^[5]

Habitat and Conservation Status[]

It is found in lowland and foothill forest and overgrown disturbed areas on Luzon. It also persists in heavily degraded forest and overgrown clearings. It is primarily a bird of forest floor and understorey, although it is sometimes also found in the middle and upper storeys. It mainly occupies forest below 500 m, although in the Sierra Madre it is locally common up to 1,000 m. Interestingly among the other striped babblers (Panay striped babbler, Palawan striped babbler and Negros striped babbler, which are all mid to high elevation species. The Luzon striped babbler is seen in lower lying areas.^[6]

IUCN has assessed this bird as near threatened 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.

References[]

• BirdLife International 2013. Robsonius rabori. 2013 IUCN Red List of Threatened Species. Downloaded on 1 January 2014.
• 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.
• Hosner, Peter A., Nikki C. Boggess, Phillip Alviola, Luis A. Sánchez-González, Carl H. Oliveros, Rolly Urriza, and Robert G. Moyle. "Phylogeography of TheGround-Warblers (Passeriformes: Locustellidae) Reveals an Undescribed Species from Northeastern Luzon, Philippines." The Condor 115.3 (2013): 630–39.
• Sánchez-González, Luis A., et al. "Nests, Nest Placement, And Eggs Of Three Philippine Endemic Birds." Wilson Journal of Ornithology 122.3 (2010): 587–591. Academic Search Premier. Web. 23 October 2014.