Western Thornbill Acanthiza inornata Scientific name definitions

8–10·5 cm; 7 g. A small, plain thornbill with pale eye. Has fine creamy-buff scalloping on forehead, fine creamy-buff streaking and spotting on ear-coverts; crown and upperparts olive-brown, slightly warmer on uppertail-coverts and base of tail; uppertail olive-brown, tinged greyish, with narrow black subterminal band; primary coverts, tertial centres and alula slightly darker brown, fine off-white edges of remiges (forming pale linear wingpanel on primaries); lores and underside creamy buff, with faint dusky scalloping or flecking on chin, throat and upper breast, flanks washed yellowish; undertail brownish-grey with faint dark subterminal band; iris cream; bill black, dark brown or grey-black, sometimes paler base of lower mandible; legs black or dark brownish-grey. Readily distinguished from congeners by combination of drab coloration, no obvious rump patch, pale eye. Sexes alike. Juvenile is similar to adult but browner above, scalloping fainter, light brown fringes of tertials and greater coverts (forming indistinct narrow wingbar); yellowish gape when very young.

SW Western Australia N to Hill R and Moora and E to Stirling Range.

Wandoo woodland, jarrah and marri forest with understorey of shrubs, also flooded gum (Eucalyptus rudis) forest, riparian formations, mallee and mixed woodland; occurs also in heathland and Banksia woodland, and sometimes in wooded parks and gardens. Seems to require shrub understorey and ground litter such as logs and woody debris. From coastal plains to low hills.

Resident, with perhaps some local post-breeding wandering. Of 65 recoveries concerning 60 individuals, all were within less than 10 km of ringing site; one recovered 6 km away one year later.

Primarily insectivorous. Food includes beetles (Coleoptera), bugs (Hemiptera), wasps and ants (Hymenoptera), and lepidopteran larvae; also takes nectar from Grevillea, perhaps an adaptation to floristically rich region in which it lives. Often seen in presumed pairs, occasionally singly or in small presumed family groups of 3–5 individuals, and can occur in flocks of up to 20; will join mixed-species flocks with A. chrysorrhoa, A. apicalis and Grey Fantail (Rhipidura albiscapa). Forages in low shrubs and trees, up to canopy level, also often on ground; terrestrial foraging may be more frequent in winter. Feeds by gleaning from foliage, and reported also as probing into bark and sallying.

Tends to be quiet and fairly unobtrusive. Song, reportedly used also as contact and in agonistic behaviour, described as “pitta-pitta-pitta”, similar to those of A. reguloides and A. iredalei but less tinkling and more constant in pitch; also as a sweet, twittered, fast “twee twee twee twee twee” mixed with “pit pit” notes, and a musical “twitchee twitchee twitchee” series interspersed with trills. Reported as mimicking Western Rosella (Platycercus icterotis), Grey Fantail (Rhipidura albiscapa) and Grey Currawong (Strepera versicolor), but this seems unusual.

Season Aug–Feb, occasionally from mid-Jul. Breeds as pair, or sometimes in group with three or four individuals attending one nest. Nest oval, domed and loosely structured, with side entrance near top, constructed from dried grasses, twigs, plant stems, rootlets, bark strips, plant down, dry leaves or flowers, bound with spider web, lined with feathers, fur or plant down, one nest was 10·8 cm tall, 7·7 cm wide, with entrance 3·2 cm across and 2·5 cm vertically; 0·6–13 m (average 4·7 m) above ground in tree or large shrub, including wandoo, marri, jarrah, casuarina (Casuarina), banksia and Hakea, or in grass-tree (Xanthorrhoea), sited against trunk in well-foliaged tree, in fork of tree or shrub, behind loose bark, in tree hollow, or among thick leaves or dense dry leaf skirt or crown of grass-tree. Clutch usually 3 eggs, laid at 2-day intervals, white to pinkish-white, freckled dark, with band around larger end; incubation by female, period 18–21 days; chicks fed by both sexes, nestling period 17–19 days. Nests parasitized by Horsfield’s Bronze-cuckoo (Chalcites basalis) and Shining Bronze-cuckoo (Chalcites lucidus); of 226 nests over 4 years at one study site, 16 (7%) were parasitized by former species and 18 (8%) by latter. Success: in one study of at least ten nests, failure rate reported as 48%; fires depress breeding rate and success through reduction of food supplies, and many pairs may not breed in year following fire. Longevity in ringing studies more than 5 years 10 months.

Not globally threatened. Locally common to uncommon. Density can reach 40 groups/100 ha, but drops after fires. Range relatively restricted, and much of the habitat being rapidly developed; this species disappears if remnant patches lose shrub understorey and ground litter. Was fairly common in King’s Park, in Perth, up to 1986, but now rare there. Fires represent a hazard for this thornbill, and fragmentation of habitat could make it more vulnerable to such predators as cats. Although currently considered to be not at risk, the species would benefit from careful monitoring, as it could become threatened.