Western Yellow Robin

Identificazione

The western yellow robin ranges between 13.5 and 15.5 cm (5+1⁄4 and 6 in) long, with a wingspan of 24–27.5 cm (9+1⁄2–10+3⁄4 in) and weight of 20 g (0.7 oz). The male and female are similar in size and coloration, with no seasonal variation in plumage. The head, neck, and upper parts are grey, with a white throat fading into a grey breast. The lores are black, the eyebrows are paler grey, and there is some faint pale streaking over the ear coverts. The underparts are yellow and clearly delineated from the breast. The rump and upper tail coverts are yellow in the nominate subspecies and olive-green in subspecies rosinae. There is a broad area of intermediate coloration between the core ranges of the two subspecies. Birds of subspecies rosinae have longer wings and tail overall, and a shorter bill and tarsus. Those from the west coast between Cliff Head and Kalbarri are significantly smaller overall. Intermediate forms between the two subspecies are found over a broad band between Lancelin and Jurien Bay southeast through the inner Wheatbelt to the coast between Denmark and Fitzgerald River National Park.<p>Juveniles have dark brownish head, neck, and upper parts coarsely streaked with creamy white. The lores are black. The chin and throat are grey-white, the breast is cream and brown, and the belly is white or off-white, tinged with brown. They molt after a few months into immature plumage, resembling adults but retaining some brownish flight feathers and secondary coverts on their wings and tail.<p>The western yellow robin produces its song with sequences of extended whistles, begun with two briefly piped notes. Its song is often heard before dawn, described as having a mournful quality, and is a familiar sound in southwest forests and woodlands. It also utters a scolding call, transcribed as ch-churr or churr-churr, and a two-syllabled zitting call. Around nesting time, the female utters a courtship or food-begging call, composed of a long note with a deeper staccato note at the end.<p>It does not resemble any other species within its range. The similar eastern yellow robin is found only in the eastern states. Immature birds closely resemble immature white-breasted robins (Quoyornis georgianus), though both are usually close by their respective parents. Young western yellow robins also have an olive tinge to the edges of their flight and tail feathers, and gain yellow feathers on their bellies as they molt from juvenile plumage.

Tassonomia

English ornithologist John Gould described the western yellow robin as Eopsaltria griseogularis in 1838, referring to a specimen collected at the Swan River Colony. The genus Eopsaltria had been introduced by English naturalist William Swainson six years earlier for what is now the eastern yellow robin (E. australis). The specific name is derived from the Medieval Latin words griseus, meaning 'grey', and gula meaning "throat". Gould reported that it was common both at the new colony on the Swan Coastal Plain and at any site with brush-like shrubs. It was included in the first collection of local fauna assembled for the newly founded Zoological Society of London in the 1830s.<p>In 1979, Western Australian ornithologist Julian Ford proposed treatment of the western and eastern yellow robin as a single species on account of similarities in calls, ecology, and behavior. Playback of one species' calls in the other's territory evoked a response. Bird taxonomist Richard Schodde did not feel that this finding warranted the lumping of the two species and concluded in 1999 that they formed a superspecies. Analyses of mitochondrial and nuclear DNA of Australasian robins in 2009 and 2011 revealed that the divergence between the eastern and western yellow robin was consistent with species-level separation, confirming their status as distinct species.<p>Amateur ornithologist Gregory Mathews described a second subspecies—Eopsaltria griseogularis rosinae—in 1912, named for Ethel Rosina White, wife of South Australian ornithologist, Samuel Albert White. Schodde observed that the delineation between subspecies does not correspond with a change in habitat and was hence valid.<p>Western yellow robin is the official name given to this species by the International Ornithologists' Union (IOC). Like all Australasian robins, it is not closely related to either the European robin (Erithacus rubecula) or the American robin (Turdus migratorius), but rather belongs in the Australasian robin family Petroicidae. The family is most closely related to the families Eupetidae (rail-babbler), Chaetopidae (rockjumper), and Picathartidae (rockfowl)—these all forming a basal lineage in the Passerida.<p>Gould called it 'grey-breasted robin' in 1848, and other names used included grey-breasted shrike-robin and grey-breasted yellow robin from the late 19th and early 20th centuries. The 'shrike-' prefix was dropped by the Royal Australasian Ornithologists Union (RAOU) in 1926. The earliest recorded name is b'am-boore—reported by English naturalist and explorer John Gilbert in 1840, and published in Gould's Birds of Australia—is derived from the Nyungar language. The orthographic or dialectal variations in the notes of colonial authors have been assessed, and a recommendation for regular spelling as bamborn and guide to pronunciation as bam'bam was proposed by Ian Abbott in 2009.

Nome scientifico

Eopsaltria griseogularis

Autorità

Gould, 1838

Ordine

Passeriformi

Famiglia

Petroicidae

Genere

Eopsaltria

Areale e habitat

In Western Australia, the western yellow robin is found south and west of an imaginary line between Kalbarri and Norseman, though it is largely absent from the coastal plain between Dongara and Rockingham. It is a rare vagrant north to Shark Bay and Toolonga Nature Reserve. Along the southern coastline, it occurs in a broken distribution to the South Australian border, at Eucla, Hampton Tableland, and the Roe Plains. In South Australia, it is found from Yalata east to the Eyre Peninsula where it extends north to the Gawler Ranges and east to Middleback Range. It is sedentary across its range.<p>The nominate Eopsaltria griseogularis griseogularis ranges along the coastal southwest Western Australia from Lancelin in the north and inland to Northam and southeast to King George Sound. Subspecies Eopsaltria griseogularis rosinae occurs from Jurien Bay and Tamala then inland across the Wheatbelt and Goldfields to the southeastern Western Australian coastline, across the Great Australian Bight and on the Eyre Peninsula.<p>Within its range, the western yellow robin is found in eucalypt forest and woodland, and mallee and acacia-shrubland in drier (semi-arid) regions. Fieldwork in the Dryandra Woodland found that it prefers locations with thicker canopy, a thicker layer of leaf litter, and logs. The latter two directly provide habitat for insects upon which the western yellow robin feeds, while the canopy makes for cooler ground temperatures (as well as more leaf litter) that are also favorable to insects. The presence of wandoo trees (Eucalyptus wandoo) and shrubs of the genus Gastrolobium also indicates thicker leaf litter. The species also avoids parts of the woodland bordering on adjacent farmland, as these areas have a thinner layer of leaf litter. In tall jarrah-marri forest, it generally remains in the midstory of bull banksia (Banksia grandis) or understory shrubs.

Migrazione

Specie stanziale

Comportamento

Comportamento migratorio: Specie stanziale.

Conservazione

Tendenza della popolazione: in diminuzione.

Tendenza della popolazione

in diminuzione