Chestnut-rumped Thornbill

The chestnut-rumped thornbill (''Acanthiza uropygialis'') is a small passerine bird in the family Acanthizidae, endemic to Australia.

Specially named for its pale-chestnut rump from mediaeval Latin ''uropygium'', the rump.Higgins, P. J., & Peter, J. M. (Eds.). (2002). ''Handbook of Australian, New Zealand and Antarctic Birds'' (Vol. 6, pp. 468-478). Melbourne: Oxford University Press.
Its other names include chestnut-tailed or chestnut-backed thornbill, tit or tit-warbler, chestnut-rumped tit or tit-warbler.
A plain, pale thornbill, with pale eyes, it is widespread throughout inland Australia, west of the Great Dividing Range to the West Australian coast but is absent in the far north and humid southwest Western Australia.Pizzey, G., & Knight, F. (2012). ''The field guide to the birds of Australia'' (S. Pizzey Ed. 9 ed.). Sydney: Harper Collins. It is a cooperative breeder like some of the other thornbills Nicholls, J. A., Double, M. C., Rowell, D. M., & Magrath, R. D. (2000). The evolution of cooperative and pair breeding in thornbills Acanthiza (Pardalotidae). ''Journal of Avian Biology, 31'', 165-176
doi: 10.1034/j.1600-048X.2000.310208.x
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Taxonomy and naming

Described and classified by John Gould in 1838 in ''Synopsis of Birds of Australia'', from a specimen collected in Liverpool Plains NSW.Gould, J. (1865). ''Handbook to the birds of Australia''. London: Published by the author

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Type, male
No17602 (525)
is in th
Academy of Natural Sciences, Philadelphia
United States. A specimen from the Gould collection is in the British Museum.

MathewsMathews, G. M. (1912). A List to the Birds of Australia. ''Novitates Zoologicae, 18'', 171-455

/ref> (1912) recognised a number of different subspecies of ''Acanthiza Uropygialis: A.u.ruthergleni, mellori, augusta, nea, murchisoni'' and ''condora'', with ''A.u.kycheringi'' added in 1922. CampbellCampbell, A. G., & Kilsyth, J. P. (1925). Thornbills of the Genus Geobasileus. ''Emu, 25''(2), 57-68
doi:10.1071/MU925057
/ref> (1925) added subspecies ''Geobasilus uropygialis moora'' and ''G.u. erema''. Where the genus ''Geobasileus'', referred to ground feeding thornbills.Campbell, A. G. (1922). Acanthiza or Thornbills. ''Emu, 22''(3), 192-199

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However, George Mack (ornithologist), MackMack, G. (1936). A systematic revision of the Australian thornbills. ''Memoirs of Museum Victoria, 10'', 86-118. retrieved 23 Oct 2013 fro
https://www.biodiversitylibrary.org/item/120023#page/90/mode/1up
/ref> (1936) and Mayr & ServentyMayr, E., & Serventy, D. L. (1938). A Review of the Genus Acanthiza Vigors and Horsfield. ''Emu, 38''(3), 244-292
doi:10.1071/MU938245
/ref> (1938) reorganised the species into two subspecies, ''A.u. uropygialis'' and ''A.u. augusta''. Recent studies do not recognise subspecies but indicate that variations in plumage colouration are clinal.Schodde, R., & Mason, I. J. (1999). ''The Directory of Australian Birds: Passerines''. Melbourne: CSIRO Publishing.Christidis, L., & Boles, W. E. (2008). ''Systematics and taxonomy of Australian birds''. Melbourne: CSIRO Publishing.

''Acanthiza'' had been previously placed in the family Pardalotidae, but are now part of the Acanthizidae.

Description

Length: 9.8 cm (9-11); wing span 15.5 cm (14-16.5); weight: 6 g.

Mid-sized thornbill similar in size and shape to inland thornbill (''A. apicalis'') and slaty-backed thornbill (''A. robustirostris'').
Pale and plain with pale iris similar to buff-rumped (''Acanthiza reguloides''), western (''A.inornata''), slender-billed (''A. iredalei'') and yellow-rumped thornbills (''A. chrysorrhoa'').

Pale grey-brown upper, rich chestnut rump and mostly black tail with pale tips, pale mottled ear-coverts and rufous suffusion on forehead and crown. Plain whitish underbody. The sexes are alike, with no seasonal variation.

Slight geographic variations, birds of the more arid inland are paler and greyer above, with a slightly paler rump patch and cleaner white below than those in coastal and subcoastal regions. May be confused with other thornbills having a rufous-brown rump patch such as brown thornbill (''A. pusilla''), inland thornbill (''A. apicalis'') and slaty-backed thornbills (''A. robustirostris'').

The chestnut-rumped thornbill is gregarious, usually in small flocks, twos or threes and sometimes with other thornbills and small passerines. Active and restless, the chestnut-rumped thornbill forages in shrubs and trees, searching briskly, flitting and hopping in foliage and low branches, probing into crevices and bark. It also hops on the ground searching among fallen debris.

Flight similar to other thornbills, cover to cover in low undulating dashes.

Voice is penetrating, with a far-carrying song of similar phrases. It also mimics other birds.

Juveniles are similar to adults, but plainer with duller head pattern, and pale buff tail tips, not white. Iris is slightly duller, cream or greyish white. Nearly fledged juveniles have pale yellow gape.

Distribution and population

Endemic to mainland Australia.

Qld: Widespread in S, to W of Great Divide, in South Western, South Central and W. South-Eastern Regions. Generally S of 23° S.Ford, J., & Parker, S. A. (1973). First record of Acanthiza robustirostris in Queensland. ''Emu, 73''(1), 27 - 27
doi:10.1071/MU973027b
/ref>Ford, J., Greensmith, A., & Reid, N. (1980). Notes on the distribution of Queensland birds. ''Sunbird: Journal of the Queensland Ornithological Society'', 11(3/4), 58-70

New South Wales, NSW & ACT: Widespread W of Great Divide, including w. slopes of Northern Tablelands and southern Tablelands, Canberra.Hobbs, J. N. (1961). The birds of south-west New South Wales. ''Emu, 61''(1), 21 - 55
doi:10.1071/MU961021
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Vic: Widespread in Mallee, Wimmera and North Districts N of 37°S.Chisholm, A. H. (1935). Birds of the Mallee National Park. ''Emu, 35''(2), 133 - 136
doi:10.1071/MU935133
/ref>

SA: Widespread in many regions, but generally absent from SE (though a few records exist).Ashton, C. B. (1985). The birds of the Aldinga-Sellicks Beach scrub. ''South Australian Ornithology'', 29(7), 169-179.Badman, F. J. (1979). Birds of the southern and western Lake Eyre drainage. ''South Australian Ornithology, 28''(3), 57-81.

WA: Generally absent from Nullarbor Plain. Farther west largely absent from south coast, widespread in areas W of 123°E from 32°S North to 22°S in Pilbara region. Widespread in Gibson Desert, and scattered sites in Great Victoria Desert.Parker, S. (1969). New and interesting distribution records of central Australian birds. ''South Australian Ornithology, 25''(3), 59-71.Sedgwick, E. H. (1949). Mixed associations of small birds in the south-west of Western Australia. ''Emu, 49''(1), 9 - 13
doi:10.1071/MU949009
/ref>

Movements

Chestnut-rumped thornbills are resident or sedentary,Brooker, M. G., Ridpath, M. G., Estbergs, J. A., Bywater, J., .Hart, D. S., & Jones, M. S. (1979). Bird observations on the North-western Nullarbor Plain and neighbouring regions, 1967-1978. ''Emu, 79''(4), 176 - 190

/ref> but some movement occurs. No large-scale movements are known, though some individuals occasionally move long distances.Baldwin, M. (1975). Birds of Inverell District, NSW. ''Emu, 75''(3), 113 - 120

/ref> Non-breeding flocks disperse before breeding.McEvey, A. R., & Middleton, W. G. (1968). Birds and vegetation between Perth and Adelaide (Results of the Harold Hall Australian Expedition, No.12). ''Emu, 68''(3), 161 - 212

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Habitat

They are found in dry woodlands and shrublands, mainly of mulga and malleeRix, C. E. (1943). A Review of the birds between the Mt. Lofty Ranges and the River Murray - a site for a real sanctuary. ''The South Australian Ornithologist, 16''(6-8), 57-78

/ref>eucalypts. Also in thickets, saltbush, bluebush, lignum, open pastoral country, among dead trees and stumps.
They occur in arid and semi-arid zones extending to temperate and subtropical zones,
in a wide variety of land forms including sand dunes, flood plains, rocky hillsides, plateaux and gorges.Ford, J., & Sedgwick, E. H. (1967). Bird distribution in the Nullarbor Plain and Great Victoria Desert region, Western Australia. ''Emu, 67''(2), 99 - 124
doi:10.1071/MU967099
/ref>Gee, P., Gee, I., & Read, J. (1996). An annotated bird list from the Davenport Range, South Australia. ''South Australian Ornithology'', 32(4/5), 76-81.

Behaviour

Feeding

Chestnut-rumped thornbills are mainly insectivores but occasionally eat seeds. Studies on stomach contents show spiders, insects, plants, seeds and buds.

They mostly forage in foliage and from branches of shrubs and low trees but also regularly on the ground, by gleaning 81.8% (leaves, twigs, branches, ground), sallying 4.4% and 13.9% by probing into bark. The young are fed tiny insects and small white grubs.Leach, H. A. C. (1928 ). The birds of Central Northern Victoria. ''Emu, 28''(2), 83 - 99

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They are gregarious and rarely seen singly. Feeding flocks are usually small parties of up to ten, and less often up to 20 birds, associating with brown thornbill (''A. pusilla''), yellow-rumped thornbill (''A. chrysorrhoa''), southern whiteface (''Aphelocephala leucopsis''), white-browed scrubwrens (''Sericornis frontalis'') or redthroats (''Pyrrholaemus brunneus''), and occasionally joined by silvereyes (''Zosterops lateralis'').

In South Australia during winter, they may congregate in mixed feeding groups with yellow (''A. nana''), yellow-rumped (''A. chrysorrhoa'') and buff-rumped thornbills (''A. reguloides''), with up to 100 or more birds in groups.

Breeding

Most records of chestnut-rumped thornbills breeding involve pairs; however, they appear occasionally to breed co-operatively.
Both adults are involved with building nests, which are small, neat and domed usually ovoid, with a rounded entrance at the side or near the top. If inside a hollow, the entrance is often flush with the opening of the hollow. Materials used are dried grass, bark strips, plant stems, moss, lichen and spider web, with a lining of feathers, wool or fur.

Nest sites are usually in hollows, often vertical, in live and dead trees, with the entrance at the end of a spout, crevice or knothole, in the side of a branch or trunk. They also nest in stumps, logs or branches lying on the ground and in fence-posts.J.N.McGilp. (1922). Birds of the Lake Frome District, South Australia. Part II. ''Emu, 22''(4), 274 - 287
doi:10.1071/MU922274
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The breeding season is June to December, and two broods, possibly three can be raised per season. The ovoid eggs are laid at two-day intervals. They are very fine, slightly glossy, flesh-white and minutely freckled all over with reddish brown and purplish brown, particularly at the large-end.Johnstone, R., & Storr, G. M. (2004). ''Handbook of Western Australian Birds'' (Vol. II). Perth: Western Australian Museum.White, H. L. (1915). Descriptions of nests and eggs new to science. ''Emu, 15''(1), 35 - 36

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The chicks are altricial and nidicolous, with both adults feeding the nestlings and fledglings.Sedgwick, E. H. (1936). Notes on the Chestnut-tailed Thornbill. ''Emu, 35''(3), 231 - 232
doi:10.1071/MU935231
/ref>Lloyd, A. (1982). Communal feeding in Chestnut-Rumped Thornbills. ''Sunbird: Journal of the Queensland Ornithological Society'', 12(2/3)

/ref> The fledging period is around 18–20 days.

Chestnut-rumped thornbills are known to be parasitised by Horsfield's bronze cuckoos (''Chalcites basalis'').Brooker, M., & Brooker, L. (2003). Brood parasitism by Horsfield's Bronze-Cuckoo in a fragmented agricultural landscape in Western Australia. ''Emu, 103''(4), 357 - 361
doi:10.1071/MU02034
/ref>

Conservation

Range: The chestnut-rumped thornbill has an extremely large range, and therefore does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation).Birdlife International. (2013). Species factsheet: Acanthiza uropygialis. Retrieved 14 Oct 2013, fro
http://www.birdlife.org/datazone/speciesfactsheet.php?id=5435
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Population trend: Though the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations).

Population size: This has not been quantified, but it is not believed to approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure).

For these reasons the species is evaluated as least concern.

However, the chestnut-rumped thornbill is on a list of declining woodland birds,Watson, D. (2011). A productivity-based explanation for woodland bird declines: poorer soils yield less food. ''Emu, 111''(1), 10 -18
doi: 10.1071/MU09109
/ref>Reid, J. R. W. (1999). Threatened and declining birds in the New South Wales sheep-wheat belt: 1. Diagnosis, characteristics and management. Consultancy report to NSW National Parks and Wildlife Service. CSIRO Wildlife and Ecology, Canberra

/ref> characterized mostly by being ground or low-shrub feeders and dwellers as well as being predominantly insectivores. The clearing of woodlands on fertile soils and overgrazing of remaining native vegetation, has resulted in fewer ground-dwelling invertebrate prey, causing chestnut-rumped thornbill's range to be possibly contracting towards the inland.

Gallery

File:Acanthiza Uropygialis, Gould, Vol 3, plate 56.jpeg, ''Acanthiza uropygialis'', Gould (1848), Birds of Australia.
File:Pair of Chestnut-rumped Thornbills.jpg, Pair of chestnut-rumped thornbills (Sturt Desert, NSW).
File:Chestnut-rumped Thornbills.jpg, Chestnut-rumped thornbills (Sturt Desert, NSW).
File:Young Chestnut-rumped Thornbill.jpg, Chestnut-rumped thornbill (Sturt Desert, NSW).

References

External links

Photos, Videos and Sounds

Graeme Chapman image of chestnut-rumped thornbill

Greg Oakley image of chestnut-rumped thornbill

Videos, Photos and sounds
on the Internet Bird Collection

Sound recording of chestnut-rumped thornbill
on Cornell Laboratory of Ornithology's Macaulay Library website

{{Taxonbar, from=Q1300729

chestnut-rumped thornbill
Endemic birds of Australia
chestnut-rumped thornbill
Taxonomy articles created by Polbot