Birdwatching in Wagga Wagga


Birds of Urban Areas: Thornbills and Relatives
July 14, 2010, 7:41 pm
Filed under: Birds of Urban Areas, Observations | Tags: , , , ,

Habitat modification is one of the major factors contributing to the ongoing decline of bird populations worldwide. Many species have quite specific habitat demands that are simply not met by cultivation and development of land. To give one prominent example, the eastern subspecies of the Brown Treecreeper (Climacteris picumnis victoriae), considered a vulnerable species, is only commonly encountered in eucalypt-dominated open woodland. (Berry Jerry State Forest, a River Red Gum Eucalyptus camaldulensis forest with a sparse understorey, seems to support the largest local population). The destruction of woodland remnants leads to the isolation of local populations and has the potential to cause local extinctions.

A few species have successfully adapted to agricultural clearing and urban development. The Sulphur-crested Cockatoo (Cacatua galerita) and Galah (Eolophus roseicapilla) are two notable examples. So successful have they been, in fact, that they threaten to overwhelm those species with which they compete for breeding sites. A third cockatoo species, the Long-billed Corella (Cacatua tenuirostris), is recovering after a long decline and is spreading at an extraordinary rate. It may soon join the list of native species with serious pest potential.

There are some species, however, that have adapted very well to urban development and should be encouraged. The thornbills (Acanthiza spp., from Gk. akanthos ‘thorn’), a group of small insectivores, are generally absent from the more built-up cities, but in Wagga are commonly seen in parks and gardens in urban and suburban areas. Two species are commonly recorded in Wagga itself and at least two others may be found in woodland remnants nearby.

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Yellow-rumped Thornbill (Acanthiza chrysorrhoa)

The Yellow-rumped Thornbill is the largest of the thornbills, measuring roughly 12cm from bill to tail. They are often seen feeding on the grouund, usually in small flocks. The spotted head is distinctive, as is the bright lemon-yellow patch on the rump. They are often noticed first by their call, a “musical, cheery, tinkling song, ending with two clear whistled notes” (birdsinbackyard.net). In a Greening Australia survey of revegetation projects in the area to the north of Canberra (Bringing Birds Back), the Yellow-rumped Thornbill was the second most-commonly seen bird, recorded only slightly less often than the Superb Fairy-wren (Malurus cyaneus).

Being a ground-feeder, they are vulnerable to predation from domestic animals, especially cats.

Yellow Thornbill (Acanthiza nana)

The Yellow Thornbill is slightly smaller than the Yellow-rumped, measuring around 10cm from bill to tail. Yellow Thornbills are dull grey-green on top and pale yellow underneath. The inland form is noticeably paler and duller than the coastal form. They spend less time on the ground than their larger cousin, opting instead to feed in trees with feathery or needle-like foliage (in native woodland they are often found in cypress-pine Callitris spp.) and small, dense shrubs. Their call is a simple, two-note ‘chip-chip’ (see birdsinbackyards.net for a recording). In the Greening Australia survey, the Yellow Thornbill was the fourteenth most-commonly recorded bird.

Two other thornbill species, the Buff-rumped Thornbill (Acanthiza reguloides) and Chestnut-rumped Thornbill (Acanthiza uropygialis), have been recorded in woodland around Wagga, though the latter has been recorded only once (its usual habitat is the arid inland). The Buff-rumped Thornbill has been recorded once on Willans Hill, but is generally found only in better-preserved woodland areas, including Livingstone National Park. The Brown Thornbill (Acanthiza pusilla) has been recorded slightly outside the Wagga area and can probably found in woodland in the area. The Inland Thornbill (Acanthiza apicalis) may also be recorded here periodically.

The Weebill (Smicrornis brevirostris) also belongs to the family Acanthizidae. It can be distinguished from the Yellow Thornbill (at close range, at least) by its much shorter bill, the white eye-ring and the paler facial markings. At around 8cm in length, the Weebill is Australia’s smallest bird. Its call is a distinctive whistle, often given as ‘wee-wit’ and ‘wee willy weetee’ (birdsinbackyards.net). The Weebill can often be seen fluttering outside the foliage of eucalypts, darting in periodically to collect food. It is rarely seen in gardens, but is common in large, well-treed parks. In the Greening Australia survey, it was the 30th most-common species.

The Western Gerygone (Gerygone fusca) and White-throated Gerygone (Gerygone albogularis) are also members of the family Acanthizidae, as are the Speckled Warbler (Chthonicola sagittata) and Southern Whiteface (Aphelocephala leucopsis). These species are not known from urban areas.

Several other small natives, including the Striated Pardalote (Pardalotus striatus), Silvereye (Zosterops lateralis) and White-plumed Honeyeater (Lichenostomus penicillatus) are found in urban and suburban area. These will be described in future posts.

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