Southern Marquesan Reed Warbler Acrocephalus mendanae Scientific name definitions

18–22 cm. A large reed-warbler, bright yellow below, with medium-length, slightly curved bill. Has whitish lores, yellow supercilium, malar and ear-coverts; feathers of crown and line behind eye deep olive to dark olive with broad fringes of pale yellowish olive; neck and upperparts yellowish olive to dark greenish olive, changing to light yellowish olive on tips of feathers of back and scapulars, then to deep buff on rump; uppertail-coverts pale brownish olive, margins more yellowish; feathers of wing and tail blackish, primaries edged light yellowish olive, secondaries broadly edged buff, both primaries and secondaries tipped yellow, upperwing-coverts broadly margined buff, rectrices tipped yellow; throat and underparts bright yellow, centre of belly white, underwing-coverts pale to bright yellow; iris dark; bill blackish brown above, horny or dull pinkish below; legs greyish or slaty. In worn plumage upperparts appear drabber and browner, as pale fringes are lost. Sexes similar. Juvenile poorly known, but is generally very similar to adult, differing principally in being paler overall, due principally to pale fringes above being more whitish or yellowish white; on Fatu Hiva (fatuhivae) dorsal surface intermediate between buffy brown and olive-brown. Races differ only in measurements and in subtle shades of colour: race dido is smaller than nominate and formerly conspecific A. percernis, but marginally larger than race A. p. idae, with a larger bill, and is the brightest race overall with less contrasting upperparts than nominate; race consobrina is very similar to nominate, but is slightly smaller than latter, especially in bill size (mean 21·5 mm, versus 23·8 mm) and has yellow of underparts marginally more intense; and race <em>fatuhivae</em> has a longer bill (mean 25·2 mm) than both A. percernis and nominate, while yellow in plumage is closest to A. percernis, but has rump and uppertail-coverts straw-yellow to bright buff, the upperparts brighter green in fresh plumage, broader and more conspicuous fringes to greater coverts and tertials, and a more frosted appearance above than 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.

Lowland plantations, e.g. of coconut, dry brushy hillsides, villages, gardens and wet upland forest, to 550 m on Tahuata, 775 m on Fatu Hiva, 830 m on Uapou and 1070 m on Hivaoa; less common in dense forest and on islands also inhabited by endemic monarchs (Pomarea spp.), reed-warblers frequent drier, low-lying and more xerophytic areas than these species.

Mainly insects, i.e. orthopterans, flies (Diptera), beetles (Coleoptera), hymenopterans, small adult lepidopterans, caterpillars, bugs (Hemiptera); also spiders (Araneae), small land snails, water crustaceans, small lizards, also some seeds, fruits and nectar. Forages in foliage and on the ground; sometimes catches insects in air.

Song of whistles, churring notes, warbles and rasping scolds, in complex and variable combinations; peak of singing activity at dusk. On Motu One, race consobrina has a simple combination of such notes uttered at frequencies of 1–4 kHz, which sounds similar to the song of A. caffer but less varied, with each sequence lasting up to seven seconds, separated by similar-length pauses. The song of race dido is reported to be similar but slower-paced. Song flight, which is well known for A. percernis on Nuku Hiva, has not been reported in the present species.

No distinct breeding season; active nests found in nearly every month, with birds in breeding condition in Jan, May and Aug–Dec and nestlings or recently fledged young recorded in Apr–Jun and Sept–Nov. Territorial, but cooperative breeding is relatively frequently recorded. Nest a massive cup of leaves, pieces of bast, pods or grasses, coconut fibres, cobweb and plant down, lined with soft delicate material, some built mainly of moss and liverworts (Hepaticae), for five nests mean external diameter 11·4 cm, height 8 cm, internal diameter 5·9 cm, cup depth 4·5 cm, situated at 1·5–25 m (chiefly 3–12 m) in fork of forest tree or sapling, e.g. Eugenia rariflora, Pandanus sp., Cordia lutea, Metrosideros collina and Ficus prolixa; territory size 50–75 m². Clutch 3–4 eggs; no information on duration of incubation and nestling periods; nestlings fed by both parents.

Not globally threatened (Least Concern). Restricted-range species: present in Marquesas Islands EBA. Abundant on five of the six major islands of the Marquesas. Race dido on Uapou was first collected in early 1920s and has an estimated current population of c. 2300 pairs (territories) within c. 80 km² of suitable habitat and density of one territory of 3·5 ha based on surveys in 1998 and 2006. On Hivaoa, nominate race occupies some 200 km² of suitable habitat, with a mean density of one territory per 4·5 ha during surveys in 2000, 2004 and 2009, with an overall abundance estimated at 4500 pairs (territories), although the species is less numerous (one territory per 7·2 ha) in areas where Common Myna (Acridotheres tristis) is numerous or that have been heavily overgrazed and degraded. On Tahuata, the same race numbers fewer than 1600 pairs (territories) based on surveys in 2004 and 2009, during which the mean density of reed-warblers was one territory per 3·14 ha. Race consobrina on Motu One (Mohotani) some 90–110 pairs were estimated in 1975, and current numbers (during surveys in 2000 and 2004) are up to c. 150 territories within an area of suitable habitat estimated at 4·6 ha. Race fatuhivae on Fatu Hiva is estimated to number fewer than 1000 pairs within c. 70 km² of suitable habitat, based on fieldwork in 2000 and 2009.