Martens's Warbler Phylloscopus omeiensis Scientific name definitions

11–12 cm. Has median crownstripe dull pale grey to bright grey with very little pale greenish admixed, especially on forehead (rarely, forehead nearly all green); lateral crownstripe greyish-black or black, either distinct almost to bill or fading out on forecrown/forehead; side of crown and nape below lateral crownstripe mainly green, with some grey along lower edge of dark stripe; ear-coverts and lores green, lores indistinctly yellow-suffused; distinct yellow eyering, sometimes diffuse anteriorly above eye; upperparts green; upperwing and tail brown-grey with green feather edges; greater upperwing-coverts with pale tips faint or lacking, sometimes showing as a distinct thin pale bar; prominent white wedges on inner webs of outermost rectrix (25·5–32 mm) and penultimate rectrix (12·5–26 mm), occasionally also a small white tip on prepenultimate rectrix; bright yellow below, variable amount of pale greenish suffusion on breast side and, often, flanks ; iris dark brown; upper mandible blackish, lower mandible pale orange; legs pale greyish-pink. Distinguished from extremely similar P. valentini by usually purer grey median crownstripe, blacker lateral crownstripes reaching farther towards bill and more clear-cut anteriorly, brighter green upperparts, more saturated yellow underparts, and on average less distinct pale wingbar; from even more similar P. tephrocephalus by larger average size, proportionately smaller bill, on average slightly less distinct head pattern, less white in tail, more often a pale wingbar, and eyering complete (not thinly broken at rear). Sexes similar in plumage, female on average smaller than male. Juvenile undescribed.

Breeds in upper part of warm temperate evergreen broadleaf forest zone, and in lower part of cool temperate zone with mainly lush deciduous broadleaf forest; favours lush undergrowth in mature forest, and secondary growth of rather low to moderate height (bushes and low trees) in relatively recently cleared areas. Has been recorded as breeding at c. 1200–2300 m (in Sichuan) and c. 1450–2200 m (in Shaanxi); almost completely segregated altitudinally from sympatric P. soror and P. valentini, but partly overlapping with P. tephrocephalus and P. intermedius. In non-breeding season in Thailand, found down to 400 m, but mainly above 1000 m, in understorey in evergreen broadleaf forest.

Migratory. Non-breeding distribution poorly known; common winter visitor to continental Thailand, arriving from late Sept, at least; found also in Cambodia in winter. Numerous on breeding grounds from late Apr, if not before.

Known to eat insects, but no studies undertaken. Forages mainly in understorey; catching of prey often involves short flights.

Song consists of short (c. 0·6–1·3 seconds) abrupt strophes of varied whistled notes either in irregular order or arranged in phrases (element groups) of 2–4 notes, each phrase given 2(-3) times (last one often incomplete at end), some strophes ending in rapid, usually single-element trills of varying length, and the strophes separated by pauses usually several seconds long; e.g. “chu-si-tsu-chu-si-tsu… pi-tsu-pi-tsu-huee-tse… huee-huee-tse-tse-tse-tse… chu-wee-chu-tsiu-tsiu-wis… tuis-tuis-tsi-tiu-huit-tiu-tsi… tiu-wee-tiu-tsi-tsi-tsi-tsi… tiu-tse-tsi-tsui-dirrrrrrrr…”; similar to song of P. tephrocephalus, but has lower proportion of trills, especially multi-element ones, fewer strophes with introductory note, and fewer phrases in non-trilled strophes; resembles song of P. burkii, but has lower proportion of phrases and multi-element trills; easily distinguished from songs of P. valentini and P. soror by e.g. presence of trills, and from that of P. intermedius by higher pitch, broader frequency span and less stuttering start. Calls with short, rather faint “chup” and doubled “chu(-)du”, sometimes also with sharp “tsip”, clearly different from calls of congeners (although double note is similar to, but harder, more clearly disyllabic and less slurred than, call of P. tephrocephalus).

No certain information, primarily as a result of previous taxonomic confusion. On basis of male singing activity, main season probably May–Jun.

Not globally threatened. Locally abundant within very small known range. No population estimates available.