Slaty-backed thornbill (Acanthiza robustirostris) belongs to the Acanthizidae family. The species is endemic to Australia. Mulga woodlands of central-western Australia are home to this thornbill. This bird forages in the same feeding zone as the flock of brown thornbills living inland. At about one to five meters above the ground, slaty-backed thornbills feed on the outer branches and foliage of shrubs and trees. In contrast to other thornbills, it feeds alone or in pairs, and does not form large foraging flocks like the Brown hornbill.
Rather than hopping along twigs and among leaves, the birds hop-glean among leaves and insects, picking off insects and larvae, often fluttering beneath foliage to do so. Many times, they forage in mixed flocks with Chestnut-tailed and Brown Thornbills. One of the most reliable identifying features of the Slaty-backed is its clean white breast. There are still many aspects of this thornbill’s biology that remain unclear. When dust bathes, it may come to the ground, although it forages mainly in mid-height foliage. Depending on the season, it may wander locally.
Mountain Thornbill (Acanthiza katherina)
It is also known as the robust thornbill, thick-billed thornbill, and robust-billed thornbill. A slaty-backed thornbill measures about 100–110 mm long. The characteristics of both sexes are similar in adults. There is a rich gray color on the upper parts with a slight blue tone, fine black streaks on the crown, and a dull russet color on the rump. The wings are a darker gray-brown color. All feathers except the central pair of the tail are dusky with white inner tips. The underparts are plain white. The eyes are red. The bill and feet are black. IMMATURES: As adults, their eyes are brown.
Slaty-backed thornbills call high, plaintive whistled seee, seee in contact. Alarm calls can also be two-note churrs. The song of the Slaty-backed thornbill is a high-pitched, up-and-down warbling, and whistled twittering, similar to that of Brown Thornbills. Nesting and breeding occur between July and November; otherwise, it depends on rainfall. The nest is usually shaped like a dome with a poorly constructed top; it is made from dried grasses and cobwebs, and it is lined with hair, feathers, and soft plant material.
The nest is usually built in the twigs and foliage of a low bush. A slaty-backed thornbill lays two or three eggs; these are white with a pink tinge, speckled finely with rust-red markings, often forming a zone at the larger end; the eggs are oblong-oval in shape, about 16 x 12 mm in size. The slaty-backed thornbill is normally found in Mulga Acacia woodlands and scrubs in the western and central parts of the mainland east, as well as in the northern Simpson Desert. There are no races.
Related Reading: Yellow-rumped Thornbill (Acanthiza chrysorrhoa)
