Marsh Grassbird Helopsaltes pryeri Scientific name definitions

12–14 cm; 11·1–17·2 g (nominate), 10·4 g (sinensis). A medium-sized warbler with boldly streaked upperparts; rather long and “full” graduated tail with feather tips pointed, becoming very ragged when worn; undertail-coverts long but, because of tail length, extend only some two-thirds of way towards tail tip. Nominate race has relatively conspicuous whitish supercilium, shading to buff on lore and towards nape, somewhat highlighted by diffuse darker eyeline from behind eye; crown brown, boldly streaked with black (forming cap), contrasting with unmarked warm brown nape; upperparts reddish-brown, boldly streaked black on mantle, back and scapulars (can appear almost black-backed in heavily worn plumage), tertial centres dark, rump and uppertail-coverts only weakly streaked (can appear unstreaked in fresh plumage); tail almost uniform reddish-brown; whitish below, whitest on chin and throat , with rufous-buff on breast side (often forming partial breastband), flanks and undertail-coverts; iris brown; bill blackish, pale pinkish basal area of lower mandible; legs pinkish-brown. Distinguished from similar Locustella certhiola mainly by much more boldly streaked mantle and back. Sexes very similar, female with weaker crown streaking than male. Juvenile has browner, less rufous-toned, plumage, browner upper mandible, yellower lower mandible, and darker irides than adult. Race <em>sinensis</em> is paler overall than nominate, upperparts more rufous-buff (less reddish-brown), tail buffish-brown, has nape streaked (rather than unmarked), also more pointed wingtip with primary P9 equal to P6/P5 (P9 = P4/P3 in nominate).

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Editor's Note: Additional distribution information for this taxon can be found in the 'Subspecies' article above. In the future we will develop a range-wide distribution article.

Breeds in wet reed-swamp . In Japan, in particular by shallow lakes where extensive beds of sedges (Carex) meet reeds (Phragmites); reeds used as songposts, nests constructed in sedges. In similar situations both in Japan and in China, gradual succession to drier habitats makes sites unsuitable for this species; where damp grassland of Japanese pampas (Miscanthus sinensis) meets reedmace (Typha) beds there is a similar but drier mix of vegetation heights, which soon becomes unsuitable. In non-breeding season extremely elusive, tending to forage low in reedbeds or tracts of dense grasses by rivers and lakes and in coastal grassland.

Japanese race (nominate) partially migratory, present in N Honshu from early May to Oct, moving to warmer Pacific coastal areas after breeding; precise extent of movement difficult to evaluate, but winter reports extend from C Honshu S to adjacent N Shikoku. Chinese race (sinensis) much more strongly migratory, so far as is known completely leaves breeding sites and moves S, with main non-breeding quarters seemingly by wetlands of lower R Chiang Jiang (Yangtze) basin; regularly recorded on passage at coast (Beidaihe, in Hebei) in May and Oct but rare, no more than two per annum during 1990s. Vagrants have reached S coast of S Korea (Cheju Cheju I in May and near Seoul in Nov).

Food consists almost entirely of small insects, chiefly larvae of moths (Lepidoptera) and flies (Diptera), which especially important food items for nestlings. Several species of bug (Hemiptera) and small beetles (Coleoptera) also known to be taken. Adept at clambering nimbly among reed stems, showing remarkable agility. Extremely skulking when not singing; if flushed, generally flies low and “weakly” for just a few metres before dropping back into vegetation.

Song , from prominent tall reed and in air, a low-pitched, repeated “djuk-djuk-djuk”; call a low “chuk”.

Begins at start of rainy season (c. 20th Jun), chicks generally fledging between mid-Jul and mid-Aug, in Japan; carrying nest material in Apr in China (near Shanghai); single-brooded, but occasional second brood suspected. One study in Japan concluded that some males were polygynous, but this is not supported by studies from at least one other site. Song display from prominent tall reed, culminating in the bird taking wing while singing, and executing several circles of an area, before dropping back to songpost. Nest in grass tussock or sedge clump, on ground or up to 35 cm above ground level, typically close to periphery of reedbed. Clutch 5–6 eggs; incubation period on average 11·3 days; fledging period c. 13–14 days.

Not globally threatened. Currently considered Near Threatened, and previously, Vulnerable. Rare and very local. Extremely skulking when not singing; as a result, passage and wintering individuals are almost impossible to view and, as such, much overlooked. In Japan, known to breed at six localities in N & E Honshu, where two independent estimates, in 1994 and 1997, were both of c. 1000 individuals (based on 500 territorial males); classed as a “Special Bird”, red-listed, and protected as a “National Endangered Species” since 1993. Many of the wetlands inhabited by this species in Japan receive some form of protection. Status in China less clear, but species known to breed in Heilongjiang (at Zhalong National Nature Reserve), in Liaoning (Shuangtai Hekou National Nature Reserve), and probably on the Wusi coast near Shanghai, which is well S of previously known range; main non-breeding grounds also protected by the Poyang Hu Nature Reserve (Jiangxi) and, to a lesser degree, by Dong Dongting Hu Nature Reserve (Hunan); it seems feasible that wetland management on some of these reserves could help to maintain healthy populations of this grassbird. Reports of its recent occurrence in summer in extreme E Mongolia (Mongol Daguur and Numrug Strictly Protected Areas) are encouraging, although perhaps may indicate further fragmentation of population. It is possible that small numbers may also breed in N Korea (and vagrants have reached S Korea). This species’ reliance on a zone of successional wetland habitat, both on breeding and on wintering grounds, requires it to be versatile enough to move to nearby sites as older habitats become too dry. Development of many shallow lakes into rice paddies is largely to blame for loss or degradation of habitat; this has happened at L Khanka (on China-Russia border), Russian shores of which now largely unsuitable.