Yellow Thornbill – The Fascinating Wonders of Woodlands and Their Inhabitants

Family: Yellow Thornbill (Acanthiza nana) is a member of the family Acanthizidae in the order Passeriformes.

Identification: Both adult sexes are similar. The upper parts are plain rich to pale olive-green; the primaries are dull brown-grey edged with olive-yellow. Tail browner, with a black bar near the tip. Also, dull white spots are over the lores, and white shaft streaks are on the cheeks. The chin and throat are yellow-washed with buff. The rest of the underparts are pale to rich yellow. The flanks are darker. The eyes are brown. The bill is pink, brown, or black. The feet are dark grey-brown. The immature birds are slightly duller.

Habitat: The fascinating yellow thornbill inhabits a range of environments, including thickets, shrublands, and forests. It is more prevalent in dry regions and favors vegetation with a predominance of casuarinas or eucalypts. The yellow thornbill color is more noticeable than that of the striated and brown thornbills, despite their similar sizes and shapes.  The harsh, clipped, double-note chips, repeated at intervals and loud for such a small bird, are the first clue to the presence of yellow thornbills. Otherwise, the birds are unobtrusive, foraging alone or in dispersed pairs or small family parties of five to eight without forming large clans as other thornbills do, and not often joining feeding flocks of mixed species.

They are almost wholly arboreal, feeding, roosting, and breeding in the mid and upper stages of woodlands, open forest, mallee, and denser eastern mulga at one to ten meters above the ground, but also foraging in bushes. Males and females appear the same because there is no sexual dimorphism. Unlike the Striated Thornbill and the similar-looking Weebill, they usually avoid eucalypts, keeping to thickets of Acacia, Casuarina, Callitris, Melaleuca, and Chenopod bushes, all trees and shrubs with bushy foliage.

There they methodically hop-glean for insects among the leaves, working quickly but remaining for some time in each shrub and calling regularly in contact and territorial defence. They are sedentary, established groups that spend the entire year in the same tiny groves of a few hectares. Although each group may only have one permanent breeding female, all members will assist in the feeding of young. Yellow thornbills have been reported in feeding flocks of up to 30 to 40 individuals, as well as mixed-species feeding flocks, on rare occasions.

Vocalizations: Yellow Thornbill calls are stereotyped as harshly clipped double-note chips, tzid-id, sometimes varied with extra chips, tzid-id, tis-tiscarrying, and repeated at regular intervals, perhaps both in contact and to advertise territory. More animated buzzing and chipping in group interactions. The yellow thornbill sounds are repeated at different intervals throughout the day and are related to bird interaction when feeding, defense, or territorial advertisement.

Nesting and Breeding: Yellow Thornbill nesting and breeding occur in August–December. Nest oval or spherical dome with a narrow entrance near the top; about 90 mm high by 65 mm across, smaller than that of Striated Thornhill. The nest is adorned with thin strips of dried bark and fine grasses· matted with cobwebs, ornamented outside with spiders’ egg sacs and green mosses, lined with fine dried grasses, plant fibers, and feathers, and placed among outer twigs or leaf clusters in acacias, native pines, or tea trees at 3–12 m above ground.

Eggs: The bird lays three eggs: flesh-white with red-brown freckles and a few lilac spots; oblong-oval, about 16 x 1 2 mm.

Distribution: Yellow Thornbill is found in groves and copses of acacia, casuarina, native pine, tea-tree, and chenopod shrubs throughout the coastal and near-inland eastern mainland, including denser brigalow and mulga scrubs. Avoids rainforest and higher, colder mountain country; infrequent in eucalypts except the black box. Visits orchards, parks, and gardens. Sedentary.

Other Names: This bird is also known as Little Thornhill, Yellow-breasted Tomtit, Yellow Dicky, and Little Tit.

Size: Yellow Thornbill measures 90–100 mm in length, has an average wingspan of 14 cm, and weighs 6–7 grams.

Status: Although the general population is decreasing, it has not yet reached the threshold of the IUCN list. Hence, it is the least concerned. Fire, land development, agricultural chemicals, and climate change have all contributed to a drop in insect populations, which could have serious consequences for a predominantly insectivorous bird in the future.

Races: There are three races.

Taxonomy: American scientist Dr. Thomas Horsfield and Irish biologist N. A. Vigors named Acanthiza nana in 1827 after observing the bird in the Sydney Cove region.