Pleske's Grasshopper Warbler Helopsaltes pleskei Scientific name definitions

16–17 cm; 16–24 g. A rather large, plain-looking <em>Helopsaltes</em> with large bill , and strongly graduated longish tail. Plumage is dull greyish olive-brown above , plain or with faint darker mottling on mantle , darker and greyer on top of head, slightly paler and browner on rump and uppertail-coverts; side of head greyish-brown, with dark lores , variable grey-buff supercilium, noticeable pale eyering; tertials and upperwing-coverts olive-brown with narrow pale grey-buff fringes, flight-feathers edged olive-brown, outermost long primary with brown outer web; tail dark brown, outer four feather pairs greyer and with buffy-white tips; off-white below, breast washed grey-buff, side of breast and flanks light greyish-brown, undertail-coverts unmarked pale warm buff; iris dark brown to orange-brown; bill dark greyish above, greyish-pink or yellowish-pink below, tinged darker towards tip; legs fleshy pink with brownish or greyish tinge. Sexes alike. Juvenile has throat and belly washed creamy or pale olive-yellow, and faint grey-brown spots across lower throat.

Has been considered conspecific with either or both of H. certhiola and H. ochotensis, but differs in voice, morphology and ecology. Molecular data reveal intraspecific structure among populations assigned to present species, while simultaneously suggesting that H. ochotensis shows remarkably little divergence (1 Drovetski, S.V., Zink, R.M., Fadeev, I.V., Nesterov, E.V., Koblik, E.A., Red’kin, Y.A. and Rohwer, S. (2004). Mitochondrial phylogeny of Locustella and related genera. J. Avian Biol. 35(2): 105–110. Close , 2 Drovetski, S.V., Semenov, G., Red’kin, Y.A., Sotnikov, V.N., Fadeev, I.V. and Koblik, E.A. (2015). Effects of asymmetric nuclear introgression, introgressive mitochondrial sweep, and purifying selection on phylogenetic reconstruction and divergence estimates in the Pacific clade of Locustella warblers. PLoS ONE 10(4): e0122590. Close ). Monotypic.

Islands in extreme SE Russia (islets in Peter the Great Bay, in S Ussuriland), S Korea (Ulleung I, off E coast, also small islands off S & W coasts) and S Japan (Izu Is, also small islands off SW Honshu and Kyushu), probably also coastal N Korea; non-breeding in coastal SE China and N Vietnam.

Breeds in damp areas with thick grasses and reeds, often with shrubs and low evergreen trees or dwarf bamboo; on exposed headlands, enclosed abandoned fields, and volcanic hill slopes up to 350 m. In non-breeding season found in coastal mangrove; also in Phragmites reedbeds and adjacent scrub.

Short-distance migrant; recorded on passage along coast of SE China. Wintering confirmed only at Hong Kong (S China) and in Red River Delta (N Vietnam), but probable throughout S China coastal regions of Fujian, Guangdong and Guangxi. Leaves breeding grounds Sept and early Oct; recorded Hong Kong from late Oct, but mainly mid-Nov to early May, with peak during Apr. Reappears on Japanese breeding grounds from early May. Lack of records in E & NE China suggests that those reaching S Korea and Russia migrate via Japanese coastline of Sea of Japan.

Insects. Forages among low cover, but ventures into open situations more often than does H. ochotensis. In S China non-breeding quarters, feeds among rocks on beaches and among leaves of water hyacinth (Eichhornia) in Hong Kong reed marsh.

Song given at night and throughout day, from prominent exposed perch and in flight, of quiet thin reedy notes followed by rather harsh drawn-out flourish, “chip-chit-chip-chir-chit-chi-schweee-scheee-scheee”, lasting c. 7 seconds; similar to that of H. ochotensis but slower-paced, with longer pauses between phrases. Call a short “chit”.

Breeds May–Jun on Izu Is (Japan); incubation recorded in June in E Russia. Has twisting display-flight between low bushes, placed on the ground. Clutch 3–6 eggs. No other information available.

VULNERABLE. Locally common, but breeding confined to small islands in W Sea of Japan and off S coasts of Japan and S Korea. Total population probably declining; estimated at no more than a few thousand individuals, although many small islands remain to be surveyed. Formerly abundant on Miyake-jima, in Izu Is, but this site experienced a major volcanic eruption in 2000; in 2003 only 300 individuals remained (half of the number present before the eruption); conservation of Japanese pampas (Miscanthus condensatus) on island recommended. Threatened by wetland destruction on wintering grounds, as well as by limited habitat loss on breeding islands. Major wintering sites are protected at Mai Po Marshes Nature Reserve, in Hong Kong, and Xuan Thuy Reserve, in N Vietnam.