Green-backed Gerygone Gerygone chloronota Scientific name definitions

9·5–11 cm, c. 6·5 g (Australian races); 7·5–8·3 cm (New Guinea races). Small gerygone with distinctive greyish head, no tail spots. Nominate race has top and side of head and neck greyish, upperparts dark greenish-olive; upperwing and tail browner, tail with faint dark subterminal band; chin, throat and underparts white, variable brownish or greyish wash on breast side, variable pale yellow wash on flanks to undertail-coverts; iris red; bill black or blackish-brown; legs black to dark grey. Sexes alike. Juvenile is similar to adult, but with diffuse off-white facial area, off-white broken eyering, upperparts duller and less green. Races differ in minor details of head coloration and yellow tone of underparts: darwini has paler head than nominate, and more buff and yellow below; New Guinea races are smaller.

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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.

In Australia, mainly riparian and monsoon vine forests and thickets, also mangroves and relict forest around sandstone outcrops, gorges and gulleys, and ecotone between mangroves and paperbark (Melaleuca) forest; sometimes in dry open eucalypt (Eucalyptus) woodland adjacent to other habitats. In New Guinea, frequents forest, gardens and secondary growth, from lowlands to c. 1500 m; mainly in hill forest, but also in monsoon and riparian forest in Trans-Fly lowlands.

Resident.

Prey includes spiders (Araneae), cockroach egg sacs (Blattodea), beetles (Coleoptera), bugs (Hemiptera), wasps (Hymenoptera) and lepidopteran larvae. Usually seen in presumed pairs or small family groups, sometimes singly; unobtrusive, seldom joins mixed feeding flocks. Forages at all heights, most often in middle to upper levels; has a liking for tall casuarinas (Casuarina) in SE New Guinea. Main method is gleaning among foliage, and also hangs upside-down to feed; sallies to catch prey, and flutter-chases, consequently disturbing prey.

Song a rapid, thin musical “choopi choopi choopi” on rising scale, repeated continuously, and a monotonous repetitive flat series continued for quite long periods when excited; in New Guinea, race cinereiceps has rather higher-pitched ascending trilling series of similar structure, each song lasting c. 20 seconds, and often repeated. Dry, quiet “chip” notes, similar to contact calls of some congeners, also given.

Little known. Recorded in Mar–Oct in Australia. Nest built by both sexes, a compact oval dome with short “tail”, side entrance near top reportedly extended into short “spout”, made of soft bark and grass and fine rootlets, thickly lined with plant fibres, plant down or feathers, often decorated on outside with spider egg sacs or lichen; suspended from branch or creepers 1·8–10 m above ground, often close to wasp nest and near water. Clutch 2–3 eggs, white, finely spotted red-brown, mainly in band around larger end; incubation probably by female alone; no information on duration of incubation and fledging periods. Nests parasitized by Little Bronze-cuckoo (Chalcites minutillus).

Not globally threatened. Fairly common but unobtrusive; easily missed if not singing. Common, but patchily distributed, in New Guinea. Local in Australia.