Scrub-birds

(Atrichornithidae)

Class Aves

Order Passeriformes

Suborder Passeri (Oscines)

Family Atrichornithidae

Thumbnail description
Small, brown, ground-dwelling birds with short wings, powerful legs, longish tail, pointed bill, and loud penetrating calls

Size
7–9 in (17–23 cm); 1–1.7 oz (30–52 g)

Number of genera, species
1 genus; 2 species

Habitat
Moist forest and thicket

Conservation status
Vulnerable: 1 species; Near Threatened: 1 species

Distribution
Limited ranges in Australia

Evolution and systematics

The two species of scrub-bird form a small monogeneric family endemic to Australia. Anatomical and molecular evidence suggest that the scrub-birds are most closely related to the lyrebirds (Menuridae), with these two families diverging from each other 30–35 million years ago. However, the broader affinities of the scrub-birds and lyrebirds are less clear and have been the subject of a long and complex debate. They exhibit a number of anatomical characteristics (particularly of the syrinx, sternum, and clavicles) that are unusual within the passerines. These characteristics have, at times, been used as an argument for placing the two families in their own suborder. It has even been argued that the anatomy of these birds indicates an affinity with the tapaculos (Rhinocryptidae) of South America. However, recent evidence from DNA analysis suggests that the scrub-birds and lyrebirds are instead related to the other endemic Australian passerine families.

Physical characteristics

Scrub-birds are small, solidly built birds, well adapted to living on the ground within extremely dense vegetation. They have stout legs, short rounded wings, and a longish graduated tail, which is often held cocked. The head has a long flat forehead tapering to a pointed triangular-shaped bill. The plumage of adults is generally brown, with fine dark barring on the upper parts. Males also have black markings on the throat and breast. Juveniles have similar plumage to adults, but slightly duller.

Distribution

Both species of scrub-bird have very restricted ranges, with the rufous scrub-bird (Atrichornis rufescens) confined to the central east coast of Australia and the noisy scrub-bird (A. clamosus) occurring only in the far southwestern corner of Western Australia. The two species are therefore on opposite sides of the Australian continent, separated by a distance of almost 2,000 mi (3,200 km) of mostly arid or semiarid lands. This current pattern suggests that scrub-birds were once distributed more widely when moist forests covered much of southern Australia during the middle Tertiary, before the continent started to dry out about 16 million years ago.

Habitat

Both scrub-bird species prefer habitat with very dense vegetation cover close to the ground, a thick layer of leaf litter, and a moist microclimate. In the case of the rufous scrub-bird, suitable habitat occurs mainly in rainforest, associated with natural or human-induced openings in the canopy, or in adjoining moist eucalyptus forest that has been well buffered from fire. The noisy scrub-bird is currently confined to coastal low forest, thicket, and heath, although historically it also occurred in moist areas within taller eucalyptus forest.

Behavior

Scrub-birds spend most of their time on, or near, the ground and are incapable of more than a few yards of sustained flight. They are, however, very adept at moving quickly through dense vegetation. Males occupy permanent territories, which they defend with remarkably loud and penetrating territorial song, particularly during the breeding season. Although territories are usually widely spaced, each individual male spends most of its time within a core area covering little more than 2.5 acres (1 ha).

Feeding ecology and diet

Both species of scrub-bird forage in leaf litter on the ground, eating a wide variety of invertebrates.

Reproductive biology

Scrub-birds are generally monogamous, with the female occupying an area on the periphery of the male's territory. The noisy scrub-bird breeds in winter, while the rufous scrub-bird breeds in spring. A domed nest is built close to the ground and is lined with a thin cardboard-like pulp of wood and grass. The clutch size is one for the noisy scrub-bird, but may be two for the rufous scrub-bird. The female incubates and feeds the young, which take three to four weeks to fledge.

Conservation status

The noisy scrub-bird was thought to have gone extinct in the late nineteenth century, until a small population was rediscovered in 1961. For many years following its rediscovery, the species had the dubious distinction of being Australia's rarest passerine. However, thanks to a highly successful program of translocation and management, the bird's status has now been reclassified from Endangered to Vulnerable. The rufous scrub-bird, while reasonably rare, has not suffered the same level of decline as that experienced by the noisy scrub-bird.

Significance to humans

None known.

Species accounts

List of Species

Rufous scrub-bird

Atrichornis rufescens

taxonomy

Atrichia rufescens Ramsay, 1866, New South Wales, Australia. Two subspecies recognized.

other common names

English: Eastern scrub-bird; French: Atrichorne roux; German: Rostbauch-Dickichtvogel; Spanish: Achaparrado Rufa.

physical characteristics

Male 7.1 in (18 cm), female 6.5 in (16.5 cm). Dark rufous-brown with fine black barring above, and buff belly. Male has black mottling on throat and breast. Bill, eyes, and legs dark brown.

distribution

Central east coast of Australia (northeastern New South Wales and far southeastern Queensland).

habitat

Patches of dense ground cover within rainforest or adjacent moist eucalyptus forest. Now mainly confined to areas above 1,968 ft (600 m) altitude.

behavior

Males defend territories using a loud "chipping" song, supplemented by accomplished mimicry of other species, particularly when disturbed. Females much less vocal, producing only soft "ticking" and "squeaking" calls.

feeding ecology and diet

Feeds on leaf-litter invertebrates obtained by turning leaves with the bill and scratching with strong legs and claws.

reproductive biology

Breeds September to November. Domed nest constructed mainly of grass, inside completely lined with cardboardlike pulp of wood and grass. Clutch size two, but one egg may be infertile.

conservation status

Listed as Near Threatened. Total population has declined markedly since European settlement, mainly due to habitat loss. Status currently being monitored by annual surveys.

significance to humans

None known.

Noisy scrub-bird

taxonomy

Atrichia clamosa Gould, 1844, Western Australia.

other common names

English: Western scrub-bird; French: Atrichorne bruyant; German: Braunbach-Dickichtvogel; Spanish: Achaparrado Occidental.

physical characteristics

Male 9.1 in (23 cm), female 7.7 in (19.5 cm); male 1.7 oz (52g); female 1.2 oz (34 g). Upperparts brown with fine dark barring. Rufous-brown on lower belly, grading to off-white on breast. Male also has black patch on upper breast and throat. Bill, eyes, and legs brown.

distribution

Far southwestern corner of Western Australia.

habitat

Low forest, thicket, and heath with dense lower stratum of shrubs and sedges.

behavior

Males employ a loud territorial song supplemented by various calls. Mimicry rarely used. Females generally silent, producing only soft calls.

feeding ecology and diet

Feeds on invertebrates, and occasionally small vertebrates, flushed from leaf litter or low vegetation.

reproductive biology

Breeds April to October. Dome nest similar to rufous scrub-bird except only lower half of inside lined with cardboard-like substance. Clutch size is one.

conservation status

Vulnerable. Recently downgraded from Endangered thanks to the success of an ongoing translocation and management program initiated over 35 years ago. Since rediscovery of the species in 1961, its total population size has been increased from less than 50 to almost 600 breeding territories.

significance to humans

None known

Resources

Books

Danks, A., A. A. Burbidge, A. H. Burbidge, and G. T. Smith. Noisy Scrub-bird Recovery Plan. Western Australian Wildlife Management Program. No. 12. Perth: Department of Conservation and Land Management, 1996.

Ferrier, S. "Habitat Requirements of a Rare Species, the Rufous Scrub-bird." In Birds of Eucalypt Forests and Woodlands: Ecology, Conservation, Management, edited by A. Keast, H. F. Recher, H. Ford, and D. Saunders. Sydney: Surrey Beatty and Sons, 1985.

Garnett, S., ed. Threatened and Extinct Birds of Australia. RAOU Report Number 82. Melbourne: Royal Australasian Ornithologists Union, 1992.

Higgins, P. J., J. M. Peter, and W. K. Steele, eds. Handbook of Australian, New Zealand and Antarctic Birds. Vol. 5, Tyrant-Flycatchers to Chats. Melbourne: Oxford University Press, 2001.

Pizzey, G. The Field Guide to the Birds of Australia. Sydney: Harper Collins, 1997.

Schodde, R., and S. C. Tidemann, eds. Reader's Digest Complete Book of Australian Birds. Sydney: Reader's Digest, 1986.

Periodicals

Bock, W. J., and M. H. Clench. "Morphology of the Noisy Scrub-bird, Atrichornis clamosus (Passeriformes: Atrichornithidae): Systematic Relationships and Summary." Records of the Australian Museum 37 (1985): 243–254.

Chisholm, A. H. "The Story of the Scrub-birds." Emu 51 (1951): 89–112, 285–297.

Danks, A. "Conservation of the Noisy Scrub-bird: A Review of 35 years of Research and Management." Pacific Conservation Biology 3 (1997): 341–349.

Sibley, C. G., and J. E. Ahlquist. "The Phylogeny and Classification of the Australo-Papuan Passerine Birds." Emu 85 (1985): 1–14.

Smith, G. T., "Habitat Use and Management for the Noisy Scrub-bird." Bird Conservation International 6 (1996): 33–48.

Webster, H. O. "Rediscovery of the Noisy Scrub-bird." Western Australian Naturalist 8 (1962): 57–59.

Other

Ferrier, S. The Status of the Rufous Scrub-bird (Atrichornis rufescens): Habitat, Geographical Variation and Abundance. Unpublished PhD Thesis. Armidale: University of New England, 1984.

Simon Ferrier, PhD