Brown Thornbill (Acanthiza pusilla) lives in eastern Australian forests across Eastern and south-eastern Australia. Its conservation status is Least Concern.
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At barely the length of a matchbox, the brown thornbill tops out at 10 cm (3.9 in) and can be as small as 9 cm, weighing only 7 g (0.25 oz). Its name even nods to its size, the Latin pusillus means "very small". That pocket-sized bird can dart through dense undergrowth.
When a raptor swoops, adult brown thornbills can copy the alarm call of the New Holland honeyeater, a sound that warns other birds of danger. This mimicry tricks predators like pied currawongs into thinking the area is already under watch, reducing attacks on thornbill nests and showing how vocal tricks can be a frontline defense.
Long-term pairs build dome-shaped nests low in ferns, using grasses, bark, moss, feathers and spider silk. They lay two to four eggs, most often three, each 16 mm × 12 mm, incubate them for 19 days and spend another 16 days feeding the chicks. Breeding runs from July to January.
A 2017 genetic study shows the brown thornbill split from its mountain cousin about 2 million years ago, a deep branch. One offshoot, the King Island brown thornbill (A. p. archibaldi), is now critically endangered, with recent surveys spotting only 20-50 birds, underscoring how isolated island populations can teeter on the brink.
Sources
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In the sun-dappled understorey of the Australian bush, the Brown Thornbill flits with restless energy, its dull brown plumage a perfect camouflage amidst the rustling leaves and tangled twigs. With a twitch of its cocked tail and a flick of its wing, it darts between the dense shrubs, its bright, inquisitive eyes ever-vigilant for the smallest insect morsels to snatch from the air. As it moves, the thornbill's tiny, melodious voice punctuates the stillness, a high-pitched whisper that weaves in and out of the rustling foliage like a hidden thread.
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