Pallas's Leaf Warbler Phylloscopus proregulus Scientific name definitions

9–10 cm; 4·5–7·5 g. A small, short-tailed and extremely active warbler with well-marked plumage. Has well-defined pale median crownstripe , equally distinct throughout its length, warm buffy yellow anteriorly, paler yellowish or whitish at rear; dark greenish brown-grey lateral crownstripe (greener at front than at rear); prominent supercilium warm buffy yellow, becoming paler yellow or whitish at rear; dark brownish-grey eyestripe sometimes “downward-hooked” at rear; ear-coverts pale buffish with pale yellowish tinge, some dusky mottling; upperparts greyish-green, well-defined pale yellow or yellowish-white rump; upperwing dark brown-grey with yellowish-green outer edges, except at bases of secondaries (which usually form contrasting dark bar); pale yellowish or greenish tips of median upperwing-coverts (usually distinct wingbar), greater coverts contrastingly dark with broad pale yellow or whitish tips (prominent wingbar); shortest and central tertials have greyish-white tips on outer webs; rectrices dark brownish-grey with yellowish-green outer edges; whitish below with a little pale yellow admixed, some dusky colour on, especially, breast side; in worn plumage duller, less yellow on head, rump and wingbars (upper wingbar often worn away, lower one narrower), often pale tertial markings worn off, also duskier and less yellow-tinged below; iris dark brown; bill blackish, lower mandible usually with small brownish-yellow or pale orange base or, rarely, mainly brownish-yellow or pale orange; legs dark brown-grey (appearing blackish), less commonly with pinkish tinge; bill and legs on average darker in non-breeding plumage than when breeding (difference perhaps age-related). Differs from P. chloronotus and P. kansuensis mainly in having yellower supercilium and median crownstripe, often also yellower ear-coverts, throat and wingbars, and compared with latter species has (on average) darker lower mandible and legs. Sexes similar in plumage, female on average smaller than male. Juvenile is very similar to adult.

SC & SE Siberia, from Altai Mts E to N Sea of Okhotsk, S to N Mongolia, NE China (Heilongjiang, E & N Jilin and N Inner Mongolia), Sakhalin and N Korea; non-breeding SE China, N Thailand and N Indochina.

Breeds in the taiga coniferous forest, including fir (Abies), spruce (Picea), pine (Pinus) and larch (Larix), or in mixed forest with high percentage of conifers; up to c. 1500–1700 m in S Russia (Sayan Mts and Tannu-Ola). Non-breeding in coniferous, mixed and deciduous broadleaf forests.

Migratory. In autumn, leaves N parts of breeding range from late Aug–Sept, and most have gone by late Sept; in S parts of range, migration peaks in late Sept and early Oct, and most are gone by late Oct. Spends winter months in S China, chiefly S of R Chang Jiang (Yangtze Kiang), and in N Thailand, N Laos and N Vietnam; arrives in Hong Kong mainly from mid-Nov. In spring, last birds leave Hong Kong in mid-Apr; passes through NE China (Hebei) early Apr to late May, peak in second half Apr/early May; arrival in S parts of breeding range from mid-Apr, more commonly late Apr to mid-May, and in N parts mainly early Jun to mid-Jun. Regular straggler W to Europe in autumn (mainly Oct–Nov), rarely in spring; vagrant also in Morocco, Israel, Turkey (1 Kirwan, G.M., Özen, M., Ertuhan, M. and Atahan, A. (compilers) (2014). Turkey Bird Report 2007–2011. Sandgrouse. 36(2): 146–175. Close ), Iran (2 Gol, S.A.T., Moody, A. and Tohidifar, M. (2014). The first record of Pallas’s Leaf Warbler Phylloscopus proregulus in Iran. Sandgrouse. 36(2): 189–190. Close ), Uzbekistan, Tadzhikistan, Bangladesh, Japan, Taiwan and USA (Alaska).

Insects, notably flies (Diptera), aphids (Aphidoidea) and small moths (Lepidoptera), also spiders (Araneae), also their eggs, larvae and pupae. Forages singly ; in non-breeding season often in mixed-species flocks. Forages both high up in canopy and in bushes; often hovers on outer edge of foliage to pick food items from leaves; prey often caught also in short flights.

Song , from concealed perch within canopy of tall tree, a loud ramble of varied clear whistles and trills, can continue without pause for up to several minutes, somewhat reminiscent of song of Island Canary (Serinus canaria), very unlike songs of its close relatives. Call, rather infrequently given, a rather faint, soft, slightly nasal “dju-ee”.

Main season Jun–Jul, nests with eggs found between mid-Jun and late Jul; one brood, in S part of range possibly two. Nest built by female, vertically elongated or rounded, with side entrance, made of dry twigs, strips of bast, other vegetation fibres, moss, tree leaves and lichen, lined with fine grass, birch (Betula) bark, feathers and hair; usually up to at least 10 m above ground in conifer, close to trunk, sometimes down to 0·5 m above ground in bush; territory in C Siberia c. 3–5 ha, occasionally up to 10 ha. Clutch 4–6 eggs; incubation by female, period 12–13 days; chicks fed by both parents, mainly by female, leave nest at 12–14 days; fed by both parents for up to one week after leaving nest.

Not globally threatened. Common to locally abundant. Common and widespread in Russia and NE China; estimated breeding densities of up to 58 birds/km² in C Siberia and 35–50 pairs/km² in SE Russia (Primorie). In non-breeding range, varies from uncommon to common in Hong Kong, and rather scarce in N Thailand; uncommon to locally common in N Indochina.