Radde's Warbler Phylloscopus schwarzi Scientific name definitions

12·5–13·5 cm; 8–15 g. A medium-sized, stocky leaf-warbler with rather large-headed, hunched appearance, stout legs and comparatively thick bill. Long, broad supercilium is buffish (and not well defined) in front of eye, becoming creamy white to rear of ear-coverts, and has dark upper border; lores and broad eyestripe dark brown, cheek and ear-coverts speckled with dark and pale brown; crown and upperparts brownish-olive (occasionally appearing lighter olive in some lights), rump and uppertail-coverts slightly greener; upperwing-coverts, flight-feathers and tail feathers brown, finely edged paler brownish-olive; dull whitish to whitish-yellow below, washed with buff on breast and flanks; undertail-coverts cinnamon-buff; iris dark brown; upper mandible brown or dark brown, lower mandible pale yellowish or fleshy-coloured; legs variable, yellowish to orange or bright yellowish-brown. Differs from P. fuscatus mainly in stockier or heavier appearance, larger head with thicker bill, slightly longer tail, thick or strong-looking orange to yellowish-orange legs, and longer supercilium broader in front of eye and frequently curving upwards on nape, and in fresh plumage buff (not whitish or whitish-buff) in front of eye; from P. armandii in slightly larger size and stouter build, supercilium broader and often less distinct in front of eye, buffish chin and throat, large or thick bill and prominently thick legs. Sexes alike. Juvenile is more olive above than adult, and has breast and belly pale yellow and flanks buff-brown.

SC & SE Siberia (Novosibirsk and Russian Altai E to Stanovoy Mts, Ussuriland, Amurland and Sakhalin), S to N Mongolia, NE China (Greater and Lesser Hinggan Mts) and N Korea; non-breeding N and C Thailand, E Myanmar (N Tenasserim) E to Indochina, occasionally SE China (Guangdong).

Breeds in open taiga forest (particularly glades and clearings) with dense undergrowth, also on hillsides with sparse forest of pine (Pinus), scattered oak (Quercus) and birch (Betula), and in larch (Larix) with similar scattered deciduous trees and rhododendrons (Rhododendron); also along edges and in open clearings, frequently in trees along streams, swamps and rivers, and in willow (Salix) thickets at lakes and riversides; avoids areas of dense forest. On passage occurs in swampy areas, river valleys with birch and willow bushes and in ditches with heavy growth of reeds or sedges. In winter in undergrowth, thick bushes, scrub and tall grassy areas, from plains to 2000m.

Migratory. All populations make post-breeding movement to SE Asia (mainly Myanmar and Thailand and Indochina, few SE China). Departs from breeding areas between late Aug and late Sept; common on passage L Baikal region in first half Sept; in E, passage through Amurland and Vladivostok area late Aug to mid-Oct, and last birds have left Sakhalin by end Sept; passage through NE China mostly completed by late Oct. Present in S parts of non-breeding quarters from Nov to late Apr/early May. Return passage in C & E China mostly May and early Jun, slightly later than migration of P. fuscatus; reaches Amurland, Sakhalin and Vladivostok area middle to late May, but in C Siberia not until early Jun or mid-Jun, and in NE Altai most arrive in second half Jun. Annual and widespread autumn vagrant in small numbers in W Europe, mostly Britain and Ireland, also SW to Malta, Morocco and Israel; vagrant also in Afghanistan, Peninsular Malaysia, India, Nepal, Bangladesh, Japan and N Philippines (Luzon).

Food mostly small insects and larvae. Forages usually alone, in low branches of trees or bushes, in ground-layer vegetation and on ground beneath dense undergrowth; normally found in canopy of trees only during breeding season. Very skulking in habits, and often remains concealed in sparse vegetation, when difficult to locate; often best detected by call.

Song, from treetop (on spring passage) or from lower parts of tree and undergrowth (later, during breeding season), a series of short and loud bursts of melodious phrases recalling those of Common Nightingale (Luscinia megarhynchos) and fast trills, “ty ty tyuk tyuk” or “pyook tuul-uul-uul-uul week-week-week-week-week” or “tyeee-tyeee-tyee-tyee- ee-ee”. Call a variably short, soft to hard, tongue-clicking “tec”, “check”, “chep” or “chack”, similar to but generally softer than that given by some Sylvia warblers and by P. fuscatus, may be repeated at fairly frequent intervals (including on passage and in wintering areas); also a soft “pwit”, “prit” or “treet” whistle with whiplash quality, recalling note of Common Quail (Coturnix coturnix), given from cover; and scolding “trrr-trick-trr” alarm, like similar call of Red-breasted Flycatcher (Ficedula parva).

Jun to early Aug; nestlings middle to late Jul in SE Russia (Amurland) and fledglings early Aug on Sakhalin I. Territorial, territory established within one week of arrival; may nest in loose groups, with several pairs in close proximity. Nest a ball of willow twigs, grass stems and fine plant fibres, placed up to 1 m from ground in dense low bush. Clutch 4–5 eggs; no information on incubation and nestling periods.

Not globally threatened. Common or locally common. Fairly common in China; common in SE Asian non-breeding area, widespread and uncommon in Cambodia. Little information on densities in breeding area; in SC Siberia, sometimes 300 birds/km² of coniferous taiga in basin of R Bolshoy Kemchug, but numbers annually variable, in some years 14–30 birds/km² in same area.