Separation from Pallas’s Grasshopper WarblerPallas’s Grasshopper Warbler is a rather variable species with three (or four) recognised (but perhaps not recognisable) races, falling into two groups: rubescens, from northern Siberia – the darkest and most cinnamon-rufous form; certhiola (including centralasiae) – the most contrastingly marked form, from south-east Siberia, north-east China, and Mongolia and the neighbouring parts of Russia and China. They share with Middendorff’s the strongly graduated tail with characteristic white tips to the retrices except for the central pair. However the commonly held misconception that Pallas’s and Middendorff’s are easily confused is dispelled if a bird is well seen.
All forms of Pallas’s differ from Middendorff’s in the prominence of the well marked blackish centres to the crown, mantle, wing coverts and tertials which are reduced to indistinct mottling on Middendorff’s with very little contrast between the feather centres and paler fringes – although subcerthiola is more strongly patterned. The rump and upper-tail coverts of Pallas’s are rufous and show dark feather centres, in particular there can be large teardrop shaped spots on the longest upper-tail coverts, although some rubescens may lack these dark centres on the upper-tail coverts.
The white notch to the inner web of the tertials, diagnostic of Pallas’s, is a somewhat variable feature in Middendorff’s and Styan’s - it is not always present on all Pallas’s. Given this degree of variability, it is of no use in the separation of Middendorff’s, Styan’s and Pallas’s Grasshopper Warblers.
Brian Small
January 2001
References:
[Locustella ochotensis ochotensis
Sylvia (Locustella) ochotensis. Middendorff, 1853. Reise Sibiriens, 2 (2): 185, pl. 16, figs.7-8. Udskoe Ostrog, lower Uda River, Udskaya Gulf, Okhotsk Sea.
Locustella ochotensis subcerthiola
Locustella subcerthiola. Swinhoe, 1874. Ibis p. 154. Hakodadi, Japan.]
Kennerley P and Leader P. Identification of Middendorff's and Styan's Grasshopper Warblers, Dutch Birding 15: 241-248, December 1993.
Nazarov Y N and Shibaev Y V. On the biology and taxonomic status of Pleske's Grasshopper warbler Locustella pleskei Tacz., new for the USSR. Trudy Zool Inst Akad Nauk SSSR, 116: 72-78, 1983
Cramp S, ed. Birds of the Western Palearctic, Vol VI, 1992. Oxford.
Swinhoe R. Birds from Hokodadi, Ibis 1874: 150-166
Measurements of Middendorff’s Grasshopper Warbler
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L. pleskei |
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