Chestnut-backed bush warbler

Chestnut-backed bush warbler
Conservation status
Least Concern  (IUCN 3.1)[1]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Passeriformes
Family:	Locustellidae
Genus:	Bradypterus
Species:	B. castaneus
Binomial name
Bradypterus castaneus (Büttikofer, 1893)
Synonyms
Locustella castaneus Locustella castanea

The chestnut-backed bush warbler (Bradypterus castaneus) is a species of Old World warbler in the family Locustellidae. Other common names include the chestnut-backed grass warbler, the cinnamon bracken warbler and the East Indian bush warbler.^[2] It is endemic to the islands of Sulawesi, Buru and Seram in Indonesia where it is found on the forest floor.

Taxonomy

Previously known as Locustella castaneus, this species has now been included in the genus Bradypterus. Three subspecies have been recognised. The nominate subspecies B. c. castaneus is known from mountainous parts of Sulawesi, B. c. disturbans is known from Buru and B. c. musculus is known from Seram Island, both in the southern Maluku Islands.^[2]

Description

The adult chestnut-backed bush warbler is a drab, unobtrusive bird about 15 cm (6 in) long. The sexes are similar. The upperparts are reddish-brown, the chin and throat pale grey, the breast deeper grey and the belly, flanks and undertail coverts various shades of brown. There is a pale streak above the eye and a dark eye-stripe. The bill is black and the legs reddish-brown.^[3]

Habitat

The chestnut-backed bush warbler is found in undisturbed primary montane forest and in secondary forest, as well as adjoining thick scrub, bushes and rank grassland. It has a preference for moss-covered rocks and tree trunks densely clad with vines. On Seram it frequents lower mountain slopes in Lithospermum and Castanopsis woodland with Shorea, Agathis and Dacrydium trees, ferns and mosses, and also dense patches of bamboo.^[3] One of the places where this bird can be found on Sulawesi is the Gunung Ambang Nature Reserve.^[4]

Behaviour

The chestnut-backed bush warbler is a mostly ground-dwelling bird, skulking in the undergrowth and running on the forest floor in a manner reminiscent of a mouse.^[4] It often flicks its wings over its back and cocks its tail slightly. It sometimes sings perched on a low branch. The song of the nominate subspecies is a repetitive series of short, insect-like buzzing trills, "tzeeeuuutzeee" and differs markedly from the song of the Seram subspecies which is a series of "zit-oh-zit" calls. The song of the third subspecies has not been recorded but is said to differ from both the others. The breeding habits of this species are unknown but a fully-fledged juvenile has been seen in August.^[3]

Status

The population trend of the chestnut-backed bush warbler appears to be steady and although it has a limited distribution, it is common in parts of its range and the IUCN has evaluated it as being of "least concern".^[1]

References