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The First Record of Spotted Bush Warbler Locustella thoracica in Thailand.

By Woraphot Bunkhwamdi, Rungsrit Kanjanavanit, Andrew J. Pierce & Philip D. Round
 
Note: This article was originally published in the Natural History Bulletin of the Siam Society 60(2) and was kindly submitted by Philip D. Round.
INTRODUCTION
Knowledge of the status of some of the unstreaked Asian warblers in the genus Locustella, formerly placed in the otherwise African genus, Bradypterus, has been confounded by past uncertainties over the identification of both museum specimens and field sightings. We document the first recorded observation of a Spotted Bush Warbler Locustella thoracica in Thailand, from Chiang Rai Province, on 27 December 2013. This is the only non-breeding season record of this species away from the north and north-east of the Indian Subcontinent and northern Myanmar (del Hoyo et al., 2006), significantly extending its presumed wintering
range. Nomenclature follows Gill & Donsker (2014).

On 27 December 2013, during a routine mist-net check by WB, a warbler was found dead in the lowest panel of a mist-net set during ringing operations at Nam Kham Nature Reserve, Chiang Saen District, Chiang Rai (20°17' N, 100° 04' E) at about 10:27 h (Figure 1). On the basis of measurements and photographs of the specimen immediately after extraction from the net it was subsequently identified as a Spotted Bush Warbler Locustella thoracica. The specimen was preserved in 70% alcohol for deposition in the Natural History Museum, National Science Museum, Thailand. The record has been accepted by the Bird Records Committee of the Bird Conservation Society of Thailand (Limparungpatthanakij et al., 2014).
DESCRIPTION
An unstreaked bush warbler with the typically strongly rounded tail and long, graduated under tail-coverts of the genus Locustella. The longest under tail-coverts were longer than the shortest outermost tail-feathers. Dark brown upperparts; grey-tinged sides of head and breast. Lower throat and upper breast grey-washed, with indistinct blackish spots or mottling. Brownish-washed flanks. Narrow whitish supercilium present but extent not specifically noted. White chin and throat, centre of lower breast and belly (Figure 1A). The individual feathers of the under tail-coverts had dark brown centres and sharply contrasting, narrow, white tips (broadest white tip 2.4 mm) (Figure 1B). Upper mandible blackish-grey, lower mandible, pale flesh with slightly dusky tip; legs pale horn. Wing length (maximum chord) 55 mm; tail 52 mm, bill (to skull) 15.6 mm; tarsus 18.9 mm. Wing strongly rounded; wing point p 4; p 2 -7.1 mm, falling roughly opposite the tips of the secondaries; p 3 -1.3 mm; p 5 -1.0 mm; p 6 -1.6 mm, p 7 -3.9 mm; p 8 -5.1 mm; p 9 -5.6 mm; p 10 - 6.4 mm. p 1 (outermost primary) 7.9 mm longer than longest primary covert (Figure 1C). Projection of primaries beyond tips of tertials 8.4 mm; p 1–p 2 = 17.6 mm; p1 to wing point 24.6 mm. Primaries 3–5 were emarginated. The primaries were numbered ascendantly—from the outermost inwards. The shortest (outermost) tail-feather was 27 mm shorter than the longest tail-feather; projection of the longest tail-feather beyond the longest under tail-covert was 19 mm.

It was noticeable that the bird had two ages of primaries. The outermost primaries, pp 1–7, were relatively fresh, having presumably been renewed earlier in the winter, whereas the innermost three primaries were old and worn.
IDENTIFICATION
The present individual was identified as a Spotted Bush Warbler on the basis of its large size (wing 55 mm), long tail which projected 19 mm beyond the longest under tail-coverts, and the narrow white edges to the under tail-coverts, following Alstrom et al. (2008). The similar Baikal Bush Warbler L. davidi is smaller and shorter tailed, with much broader white edges to the under tail-coverts, and a less strongly rounded wing. Baikal Bush Warbler (formerly considered a race, shanensis, of Spotted Bush Warbler) is a relatively common winter visitor to (mainly wetland) habitats in northern and central Thailand (Lekagul & Round, 1991; Round & Loskot, 1995) and a total of 51 have so far been ringed at Nam Kham. Two previous records of supposed Spotted Bush Warblers from northern Thailand, assigned to L. t. przevalskii and L. t. thoracica, (Deignan 1945) were shown by Dickinson et al. (2000) to be misidentified Russet Bush Warblers L. mandelli. The present record is therefore the first undoubted Spotted Bush Warbler for Thailand where, as with Baikal Bush Warbler, it is presumed to be a winter visitor. The Spotted Bush Warbler breeds from East and Central Himalayas, north and east to Central China, at elevations from 2200–3700 m (Alström et al., 2008; del Hoyo et al., 2006). The taxon L. [t.] kashmirensis of the western Himalayas is now considered to constitute a distinct species (Alström et al., 2008).
Circumstances of the find
Ringing has been implemented regularly at the privately administered Nam Kham Nature Reserve since March 2008, mainly during the months September to May, so as to primarily sample migrant and wintering birds, in collaboration with Chiang Dao Wildlife Research Station, Wildlife Research Division, Department of National Parks, Wildlife and Plants Conservation. The 14.4 ha site lies only a few km from the Mekong River and is managed primarily for reedbed and wetland birds. In the present instance, a Greater Coucal Centropus sinensis was seen flying away from the immediate vicinity of the Spotted Bush Warbler when it was found, having seemingly predated it. Some feathers were missing from the right wing but no other external injuries were evident. While an occasional predation incident may be inevitable, ringing operations are carried out by well-trained ringers who do their utmost to reduce netting accidents (there have been very few in over 2,600 handlings of birds at the site.) The value of results obtained through mist-netting, ringing and processing birds is considerable, as both the present observation and earlier observations (summarized in Pierce et al., 2013) indicate.

Figure 1. Spotted Bush Warbler Locustella thoracica, found dead, Nam Kham Nature Reserve, Chiang Saen, Chiang Rai Province, Thailand, 27 December 2013: A, ventral view. B, view to show the underside of the tail in close-up. Note the relatively long projection of tail beyond the under tail-coverts, and also the very narrow whitish edges to the latter. C, details of the wing formula. Note the relatively long outermost primary (p 1); the wing point (p 4) and the relative positions of p 3 and p 5. Photos by Woraphot Bunkhwamdi.
REFERENCES
Alstrom P., P. C. Rasmussen, U. Olsson and P. Sundberg. 2008. Species delimitation based on multiple criteria: the Spotted Bush Warbler Bradypterus thoracicus complex (Aves: Megaluridae). Zool. J. Linn. Soc. 154: 291–307.

Deignan, H. G. 1945. The birds of northern Thailand. US Nat. Mus. Bulletin 186. Smithsonian Institution, Washington, DC:

Dickinson, E.C., P. C. Rasmussen, P. D. Round, and F. G. Rozendaal. 2000. A review of the Russet Bush Warbler, Bradypterus seebohmi (Ogilvie-Grant, 1895). Systematic notes on Asian birds 1. Zool. Verh. Leiden 331: 11–64.

del Hoyo, J., A. Elliott, and D. A. Christie. 2006. Handbook of the Birds of the World. Vol 11. Old World Flycatchers to Old World Warblers. Lynx Edicions, Barcelona.

Gill, F. and D. Donsker (eds). 2014. IOC World Bird List (v 4.4). doi : 10.14344/IOC.ML.4.4.

Lekagul, B., and P. D. Round. 1991. A guide to the birds of Thailand. Saha Karn Bhaet, Bangkok.

Limparungpatthanakij, W., P. D. Round & S. Sutibut. 2014. Records Roundup, Jan-Mar 2014. BCST Bull. 31 (1): 29–36.

Pierce, A. J., W. Bunkhwamdi & R. Kanjanavanit. 2013. The first record of Common Chiffchaff Phylloscopus collybita for Thailand. Birding ASIA 20: 106–107.

Round, P. D. and V. Loskot. 1995. A reappraisal of the taxonomy of the Spotted Bush-Warbler Bradypterus thoracicus. Forktail 10: 159–172.
Kindly submitted by:

Woraphot Bunkhwamdi, PO Box 151, Chiang Mai University Post Office, Muang, Chiang Mai 50202, Thailand. Email: zo_ic@yahoo.com

Rungsrit Kanjanavanit, Lanna Bird and Nature Conservation Club, 76/1 Mu 14, Soi 5 Suthep Road, A. Muang, Chiang Mai 50200, Thailand. Email: rungsritk@gmail.com

Andrew J. Pierce, Conservation Ecology Program, School of Bioresources and Technology, King Mongkut’s University of Technology Thonburi, Bangkhunthien, Bangkok 10150, Thailand. Email: Andyp67@gmail.com

Philip D. Round, Department of Biology, Faculty of Science, Mahidol University, Rama 6 Road, Bangkok 10400, Thailand. Email: philip.rou@mahidol.ac.th
   
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