Black Grasswren | Amytornis housei

Voice

A high, fast, sustained trilling song that rings off the sandstone blocks, with sharp, dry ticking notes as contact and alarm calls. For a grasswren the sound carries well, which in this broken rocky country is often the only way to find the birds. The repertoire is less well documented than that of the southern species.

Identification

Eighteen to twenty-two centimetres, with a very long tail and a heavy, long-legged body. At a distance and in the shade of the blocks the bird simply looks black — hence the name. Close up, the black of head, throat and breast proves to be overlaid with fine white shaft streaks on the upperparts, and the back is rufous. The female shares the black head but has warm rufous belly and flanks, so a pair looks mismatched in the field. The bird runs and hops over the blocks and hardly ever flies more than a few metres.

Confusion species

Across its whole range there is no other grasswren: the nearest relative, the Carpentarian Grasswren (Amytornis dorotheae), is more than seven hundred kilometres east in the sandstone of the Gulf of Carpentaria and is far paler, rufous and finely streaked. The White-throated Grasswren (Amytornis woodwardi) of Arnhem Land is the same size and lives in the same kind of boulder country, but has a snow-white throat and upper breast that this species entirely lacks. The only other malurid commonly seen in the Kimberley is the Purple-crowned Fairywren (Malurus coronatus), which is much smaller and lives not on rock but in the pandanus and cane grass along the rivers.

Habitat

Sandstone massifs with fields of very large loose blocks and deep crevices, with hummocks of spinifex (Triodia) between them and locally small patches of thicket or monsoon forest in sheltered gorges. The blocks provide shade, cover and safe nest sites; the hummocks provide the food. It does not occur on flat spinifex country without rock.

Range and movements

Endemic to the north-west Kimberley of Western Australia: the Mitchell Plateau, the Prince Regent country, the Artesian Range and adjoining sandstone massifs. The range is small and much of the terrain can only be reached by boat or helicopter. Resident; birds stay within a single massif and do not cross the savanna in between, so the population naturally consists of isolated subpopulations.

• Resident
• dark = core range, pale = thinly spread

Where and when to look

This is not a bird you meet by chance — to see it you go deliberately to the Mitchell Plateau or one of the gorges of the north-west Kimberley, preferably early in the morning. Search along the edge of a boulder field where spinifex grows between the rocks, and let the sound guide you. The birds move over the tops of the blocks and disappear into a crevice at any disturbance; sitting still works better than searching.

Conservation

The species is listed as of Least Concern. That looks odd for a bird with so small a range, but the north-west Kimberley is one of the most intact landscapes in Australia: the country is barely inhabited, is not grazed, and the rocky terrain slows fire, so old spinifex hummocks survive between the blocks. The risks that remain are the advance of hot late-season fire on the surrounding plateaux, and feral cats. Because the entire world population sits in one landscape, the species is closely watched within Australia.

Scientific name

Amytornis housei | (Milligan, 1902)

Alexander William Milligan described the bird in 1902 as Amytis housei; because the species was later moved to another genus, the author and date are bracketed. The epithet housei honours Frederick Maurice House, the physician and naturalist who collected the first specimens as a member of the expedition that explored the north-west Kimberley in 1901. The genus was first called Amytis, after a Persian noblewoman; because that name was already taken, Leonhard Stejneger proposed Amytornis in 1885, adding the Greek ornis (bird). The name follows the field impression: a grasswren that simply looks black.