Yellow Thornbill Acanthiza nana Scientific name definitions

8·5–10 cm; 6–7 g. Small to medium-sized thornbill, the yellowest of the genus. Nominate race has forehead to hindneck olive to dull yellowish-olive (greyer when plumage worn), lores pale, narrow pale eyering (clearest at bottom of eye), ear-coverts with dense buffish-yellow brush-like streaks sometimes hint of yellowish supercilium behind eye; upperparts olive, slightly brighter on rump, yellower uppertail-coverts; uppertail brownish-olive, outer edges of rectrices yellowish, broad blackish subterminal band and olive tip; upperwing-coverts with yellow-olive fringes, outer greater coverts sometimes tipped white, fine pale edges of primaries forming pale wingpanel, contrasting with darker primary coverts and alula; chin, throat and malar area pale orange-buff, underparts yellow to bright yellowish-olive, dull yellow-olive wash on breast side, undertail-coverts yellow; undertail brownish-grey with broad blackish subterminal band; iris dark brown to red-brown; bill and legs black. Differs from superficially similar Smicrornis brevirostris in larger size, much finer and often darker bill. Sexes alike. Juvenile is duller than adult, browner on mantle, paler yellow below. Races vary mainly in minor details of measurement and plumage: flava is similar to nominate but longer-tailed, brighter in coloration, tinged yellow above, bright yellow below, orange-buff on upper breast; modesta is greyer above than others, some with brownish wash on forehead, ear-covert streaks whitish, throat darker orange-buff, underparts creamy yellow, faint olive wash on breast and flanks.

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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.

Open forest, and shrublands in drier woodland. Inhabits casuarina (Casuarina), cypress pine (Callitris), acacias (Acacia) such as mulga and brigalow, paperbark (Melaleuca), and some eucalypts (Eucalyptus), including mallee and box-ironbark. Avoids rainforest, except locally in parts of New South Wales, where found in dry monsoon rainforest and tall closed subtropical rainforest; also in coastal mangrove. Quite frequent in drier wooded shrubby parks and gardens, sometimes in exotic Monterey pine (Pinus radiata) plantations and orchards.

Primarily resident; some local movements reported, with autumn-winter post-breeding occurrences at some sites, moving into wider range of habitats. Of 389 recoveries of 278 individuals, all were less than 10 km from ringing site.

Major prey items include ants and wasps (Hymenoptera), beetles (Coleoptera), bugs (Hemiptera) including lerps (Psyllidae), flies (Diptera), also crickets (Orthoptera), lepidoptera, eggs and larvae, cockroaches (Blattodea), spiders (Araneae), and assorted other arthropods; some seeds also taken. Usually in small parties of 3–5 individuals, sometimes up to ten, and flocks with as many as 35 recorded; also singly and in presumed pairs. Almost exclusively arboreal, rarely on ground, usually in canopy and subcanopy; uses wide variety of trees and shrubs, but particularly acacia, native pine, casuarinas and paperbarks; reported as seeming to forage lower in autumn and winter than in spring and summer, using shrub layer more in winter. Forages primarily in foliage but also on bark, by gleaning, and with some aerial sallying. In South Australia recorded in mixed thornbill flocks of up to 100 or more individuals, along with A. chrysorrhoa, A. reguloides and A. uropygialis, large numbers of Silvereyes (Zosterops lateralis) sometimes joining the flock; joins mixed flocks with Smicrornis brevirostris, Striated Pardalote (Pardalotus striatus) and A. reguloides.

A repeated disyllabic “tzid-id” or “tzid- id, tiz-tiz”, rather less insect-like than that of A. lineata, more like call of Smicrornis brevirostris, given throughout day; seems to be contact call, but possibly also for territorial advertising or defence.

Season Jul–Mar (spring, summer and autumn) throughout range; sometimes double-brooded. Breeds solitarily as pair; sometimes co-operatively with helpers at nest. Nest built by both sexes, a rounded oval or nearly spherical sructure with narrow entrance near top, sometimes with loose hood over aperture, made from thin bark strips and fibres and fine grasses, matted with spider web and decorated with spider egg sacs, lichen or green moss, lined with fine dry grass, feathers, fur, wool or white silky down from seed pods or thistles, exterior may be largely bark strips, or green moss or covered with spider egg sacs, size 9–15 cm long and 5–8 cm wide, entrance diameter 2·5 cm; sited in thin leafy twigs or leaves in upper branches of shrub or small tree, sometimes fork in branch (of 74 nests in Nest Record Scheme, 33·8% in eucalypt, 8·1% in acacia and 8·1% in native pine), rarely in grass tussock, height variable, 2–12 m, sometimes to 17 m (average 6·6 m); will reuse nest for second brood. Clutch 3 or 4 eggs, sometimes 2, laid at 2-day intervals, white, finely freckled and blotched with dark, sometimes forming zone at larger end; incubation period estimated at 16–17 days; chicks fed by both parents, also by helpers if present, no information on duration of nestling period. Nests parasitized by Shining Bronze-cuckoo (Chalcites lucidus) and Horsfield’s Bronze-Cuckoo (Chalcites basalis). Success: of 22 nests, 13 (59·1%) produced at least one fledged young. Longevity in ringing studies at least 11 years 11 months.

Not globally threatened. Widespread and locally common. Race flava of far N Queensland poorly known, and occupies fairly limited range. This species suffers locally from degradation of woodland habitats and creeping suburbanization. Probably secure in most of range.