Middendorff's Grasshopper Warbler Helopsaltes ochotensis Scientific name definitions

13·5–14·5 cm; 19–23 g. Rather large Helopsaltes with subdued streaking, and well-graduated tail with pale-tipped feathers. Above, plumage is dark olive-brown with faint dusky mottling, more greyish and lightly streaked on crown, becoming tawny-brown on rump and uppertail-coverts; side of head olive-brown, with dark lores and dark eyestripe, well-marked buffish-white super­cilium; flight-feathers edged warm olive-brown, outermost long primary with whitish outer web; tertials and greater upperwing-coverts with light buffy-brown fringes; central tail feathers tawny-brown, remainder greyish-brown with whitish tips; whitish below, breast washed buffy brown, side of breast and flanks light olive-brown, undertail-coverts plain dirty whitish; iris dark brown to medium brown; bill dark greyish-horn above, greyish-pink and becoming darker towards tip below; legs dull reddish-brown to greyish-pink. Sexes alike. Juvenile has supercilium, face and underparts tinged yellow, upperparts, breast side and flanks warmer olive-brown than adult, distinct dark brown streaks on throat and upper breast.

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Has been considered conspecific with either or both of H. certhiola and H. pleskei. Hybridizes with former in E Russia (in lower Amur area and N Sakhalin), where apparently maintains stable intergrade populations, but elsewhere in range it exhibits a constant and distinctive suite of plumage, voice and behavioural characters. Birds of Kamchatka and N Kurils sometimes separated as race subcerthiola (1 Kennerley, P.R. and Pearson, D. (2010). Reed and Bush Warblers. Christopher Helm, London. Close ), but here considered indistinguishable from birds elsewhere in range. Monotypic.

E Russia (coast of Sea of Okhotsk from Magadan S to mouth of R Amur, also Kamchatka), Sakhalin, Kuril Is and N Japan (N & E Hokkaido); non-breeding Philippines and N Borneo.

Long-distance migrant. Leaves Kamchatka and other N breeding areas late Aug and early Sept, S Sakhalin by late Sept; movements continue through Oct in S Kurils, with last individuals recorded mid-Nov. Migrates mainly through Japan, apparently taking direct route to Philippines, where most arrive late Sept and Oct; some continue on to N Borneo, and recorded as vagrant (but possibly regular) in Sulawesi and E Lesser Sundas. Recorded also at Obi I, Moluccas, in Dec 2013 (2 Reeve, A.H., Mittermeier, J.C., Fabre, P.-H., Rosyadi, I., Kennedy, J.D. and Haryoko, T. (2015). New additions to the avifauna of Obi island, Indonesia, with comments on migration and breeding seasonality of Moluccan birds. Forktail. 31: 98–102. Close ). Return migration is late and rapid; remains in winter quarters to early May in N Philippines (Luzon); passage along SE China coast late May and early Jun, then continuing across Yellow Sea, Korea and Japan; first arrivals reach Amur Gulf mid-May and S Sakhalin late May, and passes through Kurils to reach Kamchatka in early Jun to mid-Jun. Overshooting spring migrants straggle to Commander Is, E Bering Sea and W Aleutian Is.

Two-part song given throughout night and much of day, from exposed perch, sometimes in flight, “drrrt-chrit-chrit-chit-cherwee-cherwee-cherwee”, lasting c. 5 seconds; similar in structure to that of H. certhiola but louder, more strident, with notes of main musical flourish more drawn out. Call a quiet “chit”.

Not globally threatened (Least Concern). Often common, and locally abundant, within its restricted maritime E Asian range. In Japan, locally common in N & E Hokkaido; further S, judged to be an uncommon passage visitor, though frequently overlooked. Uncommon to rare on Sakhalin I. Uncommon winter visitor to Philippines.