Yellow Thornbill

The Yellow Thornbill, Acanthiza nana, is a diminutive passerine bird, once known as the Little Thornbill. It is characterized by its vibrant yellow plumage, which is particularly prominent compared to its relatives, the Striated and Brown Thornbills. Both sexes are identical in appearance, lacking sexual dimorphism, and they measure approximately 9 cm in length with a wingspan of 14 cm, and a weight range of 6–7 grams.

Identification Tips

Adult Yellow Thornbills exhibit greenish back feathers and olive-brown wing coverts with paler edges on the primaries, contrasting with the alula. The upper and under-tail coverts are duller, matching the wings except for a dark brown-black subterminal band. Their throat and chin are a pale buff-orange, transitioning into a soft, creamy-yellow breast. Their legs, toes, and bill are black, and their eyes are dark brown, often encircled by a grey or pale brown outer ring. A narrow, cream eye-ring and similarly colored lores with a slight grey tone are also present.

Habitat

These birds inhabit temperate and semi-arid regions, occasionally extending into subtropical zones. They favor shrublands, forests, and thickets dominated by casuarinas or eucalypts, particularly in drier climates.

Distribution

The Yellow Thornbill is endemic to the eastern coast of Australia, with a range that spans from northern and central west Queensland, through much of New South Wales, across Victoria and the Australian Capital Territory, and into the southeastern corner of South Australia.

Behaviour

Yellow Thornbills are often observed in small groups or pairs, though they can occasionally join feeding flocks of up to 35 individuals or mixed-species flocks. They are agile foragers, moving rapidly through the upper and middle levels of the forest canopy, searching for food under bark or catching insects in flight.

Song & Calls

The species is known for its loud, two-note 'tzid-id' call, which is harsher and less insect-like than that of the Striated Thornbill. This call serves various purposes, including contact between birds, defense, and territorial advertisement.

Breeding

Breeding typically occurs in solitary pairs, although there is some evidence of cooperative breeding. Their domed nests, with a small entrance near the top, are constructed from bark-fiber and grasses bound with spider-web in the upper foliage of shrubs and small trees. Clutches usually consist of two to four eggs, which are incubated for 16–17 days.

Diet and Feeding

Yellow Thornbills primarily consume insects but may also eat seeds. They exhibit a preference for foraging in the upper and middle canopy levels and are adept at catching insects mid-flight.

Conservation Status

The IUCN Red List classifies the Yellow Thornbill as Least Concern, but notes a decreasing population trend. Factors such as fire, land development, agricultural practices, and climate change have been implicated in the decline of both their habitat and insect prey.