ID Guide: Spotted Bush Warbler and Baikal Bush Warbler

Spotted Bush Warbler
Spotted Bush Warbler Locustella thoracica, Sichuan, China, July. Read this post to learn about Spotted Bush Warbler and its closely related congener Baikal Bush Warbler L. davidi. (Craig Brelsford)

by Craig Brelsford
Founder, shanghaibirding.com

SPOTTED BUSH WARBLER

Spotted Bush Warbler Locustella thoracica inhabits Himalayas and central Chinese mountains, from southeast Tibet and northern Qinghai east across northern Yunnan to Guizhou and southern Gansu and northern Sichuan to the Qin Mountains in Shaanxi. HABITAT & BEHAVIOR In thickets and dense scrub in forest glades and alpine meadows, in summer to 4300 m (14,110 ft.), lower in winter. Shy, but breeding males sing conspicuously. ID & COMPARISON Similar to Baikal Bush Warbler L. davidi and Russet Bush Warbler L. mandelli. Breeding adult rufous-brown from forecrown to graduated tail. Crown and mantle faintly scaled. Short, narrow dull-grey supercilium conspicuous before eye, fainter behind; dark eye-stripe also most distinct before eye. Ear coverts ashy-grey. Chin whitish. Lower throat and upper breast washed grey and spotted black; distinctiveness of spotting varies by individual and season (may be totally obscured in non-breeding plumage) but usually weaker than Baikal Bush Warbler. Flanks and undertail coverts tawny brown, the latter boldly scaled white. Juvenile washed yellowish below and has weaker, yellow-tinged supercilium. Brown Bush Warbler L. luteoventris lacks scaling on undertail coverts and never has grey wash on breast. Russet Bush Warbler has russet ear coverts and a less prominent supercilium. BARE PARTS Bill black; legs bright orange-pink. VOICE Song a fast, streaming “trick-he-dee, trick-he-dee, trick-he-dee,” the sequence repeated continuously for several minutes; delivered also in winter. Baikal, Russet, and Chinese Bush Warbler L. tacsanowskia have a very different, buzzing song. — Craig Brelsford

BAIKAL BUSH WARBLER

Baikal Bush Warbler
Baikal Bush Warbler Locustella davidi davidi, Inner Mongolia, China, July. (Craig Brelsford)

In China, Baikal Bush Warbler Locustella davidi davidi breeds in the northeastern provinces plus Hebei, Shanxi, Shaanxi, and Sichuan. Both davidi and Siberian breeder suschkini are rarely recorded passage migrants in China, with suschkini migrating east of Tibetan Plateau and davidi more numerous in coastal provinces. Winters Southeast Asia, rarely southeast China. HABITAT & BEHAVIOR In thickets and dense scrub in taiga glades, along streams, and at edges of fields, to 1400 m (4,590 ft.). Shy and difficult to observe. ID Breeding adult rufous-brown from forecrown to tail, lighter than Spotted Bush Warbler L. thoracica and distinctly warmer than Chinese Bush Warbler L. tacsanowskia. Short, whitish supercilium brighter and more prominent than Spotted and Chinese. Has dark eye-stripe, lacking in Chinese and Russet Bush Warbler L. mandelli. Ear coverts dull brown (not ashy-grey as in Spotted), contrasting little with crown and upperparts. Chin whitish. Lower throat and upper breast washed brown (not grey, as in Spotted) and streaked black; distinctiveness of streaking varies by individual and season (may be totally obscured in non-breeding plumage) but is usually stronger than Spotted and Russet and especially Chinese. Flanks washed brown. Undertail coverts dark brown and boldly scaled white (Brown Bush Warbler L. luteoventris lacks scaling). Juvenile has yellowish wash below and on supercilium. BARE PARTS Bill all-black in breeding season, yellow on lower mandible outside breeding season (Spotted all-black in all seasons); legs bright orange-pink. VOICE Song, delivered also in winter, an insect-like, raspy buzz, far different from Spotted. See sound-recording below. — Craig Brelsford

SOUND-RECORDING

Baikal Bush Warbler, Inner Mongolia, July (0:21; 4 MB; Craig Brelsford)

PHOTOS

Bush Warblers
The dull-brown ear coverts of Baikal Bush Warbler Locustella davidi davidi (L) contrast little with the crown and upperparts. In Spotted Bush Warbler L. thoracica (R), the ashy-grey coverts show a more marked contrast. (Craig Brelsford)
Spotted Bush Warbler
Spotted Bush Warbler perching conspicuously on bamboo, Mt. Wawu, Sichuan, July. Breeding season offers birders a chance to view this normally shy and elusive species. (Craig Brelsford)
Spotted Bush Warbler
Dorsal view of Spotted Bush Warbler. Note the ‘dark, russet brown’ upperparts and the ‘dull grey supercilium, most conspicuous in front of eye but merging with crown sides behind’ (Kennerley & Pearson 2010, 159). (Craig Brelsford)
Baikal Bush Warbler
Baikal Bush Warbler, Greater Khingan Range, Inner Mongolia, July. Note the buffy white supercilium and warm brown flanks. (Craig Brelsford)
bamboo-wawu
Spotted Bush Warbler habitat on Mt. Wawu (29.648976, 102.951520), elev. 2700 m (8,860 ft). Breeding Spotted Bush Warbler favors ‘rank herbage by forest clearings and alpine meadows’ (Madge 2006, 602) and ‘grasslands and pastures interspersed with low scrub and thickets, including bamboo’ (Kennerley & Pearson 2010, 160). In rich, little-disturbed bamboo seas such as this, Spotted Bush Warbler can occur in high densities. Its congener Brown Bush Warbler Locustella luteoventris also breeds here, as does Aberrant Bush Warbler Horornis flavolivaceus. Brown Parrotbill Cholornis unicolor occurs year-round. (Craig Brelsford)
Baikal Bush Warbler habitat
Baikal Bush Warbler habitat in Greater Khingan Range, Inner Mongolia (50.719844, 121.995758), elev. 820 m (2,690 ft.). Baikal Bush Warbler breeds in ‘grassy meadows with a scattering of trees and bushes,’ often near streams (Kennerley and Pearson 2010, 166). Among the other species using this rich habitat are Pallas’s Grasshopper Warbler Helopsaltes certhiola and Radde’s Warbler Phylloscopus schwarzi. (Craig Brelsford)

RESOURCES ON LOCUSTELLA AND HELOPSALTES WARBLERS

Click the links below for coverage on shanghaibirding.com of locustellid warblers.

Gray’s Grasshopper Warbler Helopsaltes fasciolatus
Marsh Grassbird H. pryeri
Pallas’s Grasshopper Warbler H. certhiola
Middendorf’s Grasshopper Warbler H. ochotensis
Lanceolated Warbler L. lanceolata
Brown Bush Warbler L. luteoventris

ACKNOWLEDGEMENTS

Daniel Bengtsson served as chief ornithological consultant for my Photographic Field Guide to the Birds of China, from which the species descriptions above are drawn.

BIBLIOGRAPHY

Alström, Per, Pamela C. Rasmussen, Urban Olsson, and Per Sundberg (2008). Species delimitation based on multiple criteria: the Spotted Bush Warbler Bradypterus thoracicus complex (Aves: Megaluridae). Zoological Journal of the Linnean Society, 154: 291–307. Available at https://www.shanghaibirding.com/wp-content/uploads/2019/02/Alstrom-et-al.-2008-Bradypterus-thoracicus-ZJLS.pdf (accessed: 8 Aug 2020).

Brazil, Mark (2009). Birds of East Asia. Princeton University Press, New Jersey.

eBird (2020). eBird: An online database of bird distribution and abundance [web application]. eBird, Cornell Lab of Ornithology, Ithaca, New York. Baikal Bush Warbler in China (https://ebird.org/species/spobuw1/CN). Spotted Bush Warbler in China (https://ebird.org/species/spobuw3/CN). Accessed: 27 Apr 2020.

Kennerley, P. & Pearson, D. (2010). Reed and Bush Warblers. London: Christopher Helm.

MacKinnon, John & Karen Phillipps (2000). A Field Guide to the Birds of China. Oxford University Press.

Madge, S.C. (2006). Family Sylviidae (Old World Warblers). Pp. 602-3 (Spotted Bush Warbler, Siberian Bush Warbler) in del Hoyo, J., Elliott, A. & Christie, D.A. eds. (2006). Handbook of the Birds of the World. Vol. 11. Old World Flycatchers to Old World Warblers. Lynx Edicions, Barcelona, Spain.

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