|Australian Bush Birds|
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|Buff-rumped Thornbill - Acanthiza reguloides|
|The Buff-rumped Thornbill initially appears to lack distinctive marks but closer examination shows the pale eye, speckled face and other identification features.|
The Buff-rumped Thornbill - Acanthiza reguloides - is a small (10 to 11 centimetres) generally brown bird found in slightly different coloured versions depending on whether they are in the northern or southern part of the distribution. Male and female are similar. The eye is pale, sometimes described as greyish-white, the bill is dusky brown, paler below, feet are dusky grey.
Upper parts are dark olive-brown in the south to mid olive-green in northern populations; rump and base of tail are dull pink-cream buff in the south to mid-yellow in the north. Tail is dusky black with narrow buff tips in the south top pale yellow tips in the north; the central pair do not have coloured tips. Forehead and face are scalloped and flecked buff-white in the south to yellowish cream in the north; brow is reddish. Underparts are buffy cream flecked grey on the throat and side of the breast in the south and plain yellowish cream in the north. Colour deepens on the flanks.
|Buff-rumped Thornbill - page 2|
Immature birds are duller in colour and lack distinct marking on the face and forehead. Juveniles have dark-coloured eyes. Immature plumage moults out at the first autumn moult, about three months after fledging.
Buff-rumped Thornbills are birds of dry, open eucalypt forest and heath woodlands of the east coast and nearby ranges. Distributed from the Atherton Tableland in Queensland to the Mount Lofty Ranges in South Australia, extending inland to the western slopes of the mountain ranges.
Where the understory is shrubby the birds spend much time on the ground among the litter and on rough-barked tree trunks, hopping about in small groups gleaning a range of small insects and sometimes seeds. Further north, in Queensland, where the ground is covered with tall grasses, the birds forage higher in the smaller trees up to 20 metres above the ground.
Sedentary birds forming local clans of up to 20 birds which merge breeding territories to form a large clan territory of about 15 hectares. Each clan mixes with other insectivorous species but expels other clans of its own species. The keep up constant twittering to maintain contact as they work through the territory each day.
Described as an uncommon bird with sedentary, but patchy, distribution
Breeding takes place between August and December. Clans break up into breeding units of a single female and one to three males in small nesting territories. The female builds a nest of a dome of grasses and bark strips bound with cobwebs; lined with feathers, fur or hair; The nest is built in or under a shrub or low tree, under bark on the side of a tree trunk or in a hollow in the ground beneath tussocks.
Three to five eggs are laid, usually four; flesh white, with tiny freckles and larger spots of pale red to rich red-brown,often forming a zone at the larger end. Oblong-oval, about 16 by 12 millimetres. The female incubate alone but all members of the breeding unit share in feeding the young. Most foraging is then done in trees at this stage. After fledging the young remain with the clan until the next spring breeding season, young males then join their parents breeding group while young females migrate out of the area.
Variation of colour scheme on a south to north basis has led to some naming schemes including four sub-species.
¶ reguloides from central Victoria through New South Wales to the Queensland border.
¶ australis from central Victoria west into South Australia.
¶ nesa in south-east Queensland between the NSW border and about Rockhampton.
¶ squamata north of about Rockhampton; this sub-species has a greener back and predominantly pale yellow underside.
Not all of these suggested sub-species have been widely accepted although there appears to be wider acceptance of the north Queensland sub-species squamata.
¶ Genus Acanthiza is in Family Acanthizidae with Scrubwrens, Heathwrens, Gerygones, Whiteface and other Thornbills.