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LITTLE-KNOWN ASIAN BIRDS
The Philippine ‘ground warblers’ ROBERT HUTCHINSON & ABDELHAMID BIZID One of the Philippines’ most elusive species was first collected by D. S. Rabor in the Cordillera Mountains, north-west Luzon, as recently as 1959 and described by Rand (1960): a medium-sized, ground-dwelling passerine which they named Napothera rabori, believing it to be related to the Napothera babblers of South-East Asia. Specimens subsequently collected in the Sierra Madre, northeast Luzon, were included in N. rabori; however, specimens from Sorsogon province in the far south of Luzon were sufficiently different to be separated as N. sorsogonensis (Rand & Rabor 1967). Subsequently, DuPont (1971a,b) lumped the two as a single species, Luzon Wren Babbler, which he named N. r. mesoluzonica, because he believed that one specimen from Laguna province, central Luzon, was intermediate between the other taxa, despite the only specimens from the northern populations being immature. Dickinson et al. (1991) retained them as a single species, but preferred the English name Rabor’s Wren Babbler, which was subsequently followed by Kennedy et al. (2000). On 16 January 1990, Lambert (1990) recorded two at Angat watershed, south-west Sierra Madre mountains between 250–300 m—the first seen in the field since the description of the species in 1960 from three trapped specimens. On 5 and 6 March 1990, de Roever (1990) saw a single bird in Quezon National Park, Laguna province, and contributed a description and sketch showing the stance/ posture it adopted—notably the way it cocked its tail. Sightings in the field continued to be infrequent and it was not until between December 1993 and February 1994 that the insect-like song was recorded at Angat where at least three individuals were heard, whilst four birds were seen and another three heard in Quezon, where on 25 February 1994 two adults were seen feeding a begging recently fledged juvenile (Harrap & Mitchell 1994). The few ornithologists fortunate enough to observe the species in the field (e.g. Lambert 1993, Harrap & Mitchell 1994) had noted that the behaviour and song did not resemble other Napothera taxa, but it was Collar (2006) who, on morphological grounds, took the first steps towards unravelling the true taxonomic status of the species by establishing an endemic genus Robsonius. Collar also returned to Rand & Rabor’s (1967) treatment as two species R. rabori and R. sorsogonensis (the latter including mesoluzonica), naming them Rustyfaced and Grey-banded Babbler respectively.
Oliveros et al. (2012) not only confirmed the validity of Robsonius but also revealed that it was most closely related to the Locustellidae and coined the name ‘ground warblers’ for the genus. The final twist in the taxonomic saga came when Hosner et al. (2013) found that the populations from the Cordillera Central and Sierra Madre are actually different species, previously unnoticed because R. rabori (sensu stricto) had been known from just the single juvenile halotype. Their work, supported by molecular phylogenetics, established that the Sierra Madre harbours a new taxon which they named Sierra Madre Ground Warbler R. thompsoni, with English names of Cordillera Ground Warbler for R. rabori and Bicol Ground Warbler for R. sorsogonensis, following WBCP (2014); the latter no longer includes mesoluzonica, which was found to be an invalid taxon. The three taxa are nicely illustrated in Plate 1. As a result of the extremely skulking and elusive nature of all three species, there are very few images available and none had ever been captured on camera in the field. The only images on OrientalBirdImages (www.orientalbirdimages.org) are of a trapped individual of R. thompsoni in the hand, obtained by J. C. T. Gonzalez on 8 August 2009 during fieldwork for a completely different project at Palanan, Sierra Madre, Isabela province (Plate 2). Gonzalez has commented: I had seen two more adults running across the forest floor in the short undergrowth and between the large bole/ trunks of dipterocarps. Sadly, I was unable to get images of the two birds because I was mesmerized by their antics, one even stopped and stood on top of tree root and did a quick sweep—much like meerkat sentinels are known to do—before running off. As they ran, they had a rather unusual posture, a bit crouched like a shy roadrunner. Finally on 10 April 2014, AB obtained a series of images of Sierra Madre Ground Warbler on Mount Cabulao, Sierra Madre, Aurora province (Plate 3). Whilst on 26 March 2014, in the north of the Cordillera Central, near the town of Adams, Ilocos Norte province, RH made the first field observations of Cordillera Ground Warbler since its true taxonomic position was established. On a forest slope above the road with relatively open understorey, two birds were observed, standing about 30 cm apart and both giving the typical highpitched insect-like song of the species group, holding their bodies upright and their bills pointing
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ILLUSTRATION BY MARCO PINEDA, REPRODUCED WITH PERMISSION
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Plate 1. Top: Bicol Ground Warbler Robsonius sorsogonensis, centre: Sierra Madre Ground Warbler R. thompsoni, bottom: Cordillera Ground Warbler R. rabori.
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The Philippine ‘ground warblers’
reference on the species’s original discovery. Bram Demeulemeester is thanked for invaluable field assistance in AB’s successful quest to photograph R. thompsoni and thanks go to J. C. Gonzales for his behavioural observations.
J. C. T. GONZALEZ
References
ABDELHAMID BIZID
Plate 2. Sierra Madre Ground Warbler, trapped at Palanan, Sierra Madre, Isabela province, 8 August 2009.
Plate 3. Sierra Madre Ground Warbler, Mount Cabulao, Sierra Madre, Aurora province, 10 April 2014.
directly skywards, each with its tail cocked at about 45°. The performance continued for at least 2 minutes before the birds moved slowly away up the slope. As the species shows no sexual dimorphism it is impossible to say if this was a territorial interaction between rival males or the courtship display of a pair. Acknowledgements Peter Hosner is thanked for providing information on the University of Kansas expedition to Adams which rediscovered the species there, enabling RH to successfully observe R. rabori in the field. Christian Perez kindly provided background
Dickinson, E. C., Kennedy, R. S. & Parkes, K. C. (1991) The birds of the Philippines: an annotated check-list. Tring UK: British Ornithologists’ Union (Checklist 12). DuPont, J. E. (1971a) Notes on Philippine birds (No.1). Nemouria 3: 1–6. DuPont, J. E. (1971b) Philippine birds. Greenville, USA: Delaware Museum of Natural History (Monogr. 2). Collar, N. J. (2006) A partial revision of the Asian babblers (Timaliidae). Forktail 22: 85–112. Harrap, S. & Mitchell, K. (1994) More notes on Rabor’s Wren-Babbler Napothera rabori. Oriental Bird Club Bull. 20: 50–51. Hosner, P. A., Boggess, N. C., Alviola, P., Sanchez-Gonzalez, L. A., Oliveros, C. H., Urriza, R & Moyle, R. G. (2012) Phylogeography of the Robsonius ground-warblers (Passeriformes: Locustellidae) reveals an undescribed species from northeastern Luzon, Philippines. Condor 115: 630–639. Kennedy, R. S., Gonzales, P. C., Dickinson, E. C., Miranda, Jr., H. C. & Fisher, T. H. (2000) A guide to the bird of the Philippines. Oxford: Oxford University Press. Lambert, F. R. (1990) Recent reports: Philippines, Luzon. Oriental Bird Club Bull. 11: 46. Lambert, F. R. (1993) Some key sites and significant records of birds from the Philippines and Sabah. Bird Conserv. Internatn. 3: 281–297. Moyle, R. G., Andersen, M. J., Oliveros, C. H., Stienheimer, F. & Reddy, S. (2012) Phylogeny and biogeography of the core babblers (Aves: Timaliidae). Syst. Biol. 61: 631–651. Oliveros, C. H., Reddy, S. & Moyle, R. G. (2012) The phylogenetic position of some Philippine þbabblers’ spans the muscicapoid and sylvioid radiations. Mol. Phylogenet. Evol. 65: 799–804. Rand, A. L. (1960) A new species of babbling thrush from the Philippines. Fieldiana Zool. 39: 377–379. Rand, A. L. & Rabor, D. S. (1967) New birds from Luzon, Philippine Islands. Fieldiana Zool. 51: 85–99. de Roever, J. (1990) Notes on the Luzon Wren-Babbler. Oriental Bird Club Bull.12: 33–34. WBCP (Wild Bird Club of the Philippines) (2014) Checklist of the birds of the Philippines. Accessed from http://birdwatch.ph/ on 27/03/2015.
Robert HUTCHINSON 26 Sutton Avenue, Chellaston, Derby DE73 6RJ, UK Email:
[email protected] Abdelhamid BIZID Email:
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