First Record of Spotted Bush Warbler Locustella thoracica
By Woraphot Bunkhwamdi, Rungsrit Kanjanavanit, Andrew J. Pierce &
Philip D. Round
This article was originally published in the Natural
History Bulletin of the Siam Society 60(2) and was kindly submitted
by Philip D. Round.
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).
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.
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
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.
Alstrom P., P. C. Rasmussen, U. Olsson and P. Sundberg. 2008. Species
delimitation based on multiple criteria: the Spotted Bush Warbler
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Dickinson, E.C., P. C. Rasmussen, P. D. Round, and F. G. Rozendaal.
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Woraphot Bunkhwamdi, PO Box 151, Chiang Mai University Post Office,
Muang, Chiang Mai 50202, Thailand. Email: firstname.lastname@example.org
Rungsrit Kanjanavanit, Lanna Bird and Nature Conservation Club,
76/1 Mu 14, Soi 5 Suthep Road, A. Muang, Chiang Mai 50200, Thailand.
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: email@example.com