Buff-sided Robin

Identification

The buff-sided robin is a medium- to large-sized robin species, with body length ranging from 16 to 18 cm (6.3 to 7.1 in). Adult buff-sided robins are not sexually dimorphic, and the sexes cannot be differentiated on the basis of plumage. However, males are generally larger than females with very little overlap for weight, head length, bill length, tarsus and wing cord length; and sexing criteria can be developed on the basis of combined morphological measurements.<p>Based on data from museum specimen labels, adult wingspans range from 84 to 93 mm (3.3 to 3.7 in) (n=22) in male birds to 77 to 85 mm (3.0 to 3.3 in) in female birds (n=17). Adult male buff-sided robins weigh between 20.0 to 25.5 g (0.71 to 0.90 oz) (n=13), and females weigh between 15.5 to 20.3 g (0.55 to 0.72 oz) (n=10). Adult tarsus length ranges from 20.4 to 24.0 mm (0.80 to 0.94 in) (n=22) in male birds to 18.6 to 20.7 mm (0.73 to 0.81 in) in female birds (n=17).<p>The head and neck of adult birds is characterised by a dark hood with a prominent white stripe on the supercilium, the lores and auriculars are black, the malar region white, the throat white and rictal bristles are prominent. The mantle and nape are dark olive-brown to black, the chest has a strong grey wash, and the flanks and sides are deep fawn, becoming almost white on the belly. The base colour of the wings is dark brown to black, while the extremities of the greater wing-coverts, base of the primaries, base and extremities of the secondaries, and extremities of the tail are white. The bill is black, and the legs and feet are grey to blackish-brown or brown to black. The iris is dark brown. Distinguished from the similar white-browed robin by its larger size, thicker and longer white superciliary stripe, duskier upper back, broad black face band, grey chest, broader white remigial bar, rich tawny to rufous flanks, and white tipping on all rectrices.<p>In juvenile plumage, the head, neck and upper body are rusty brown with faint barring of light cream, the back is dark brown, upper wing-coverts white with buff tips, with a narrow white bar on the bend of the wing, white tipping on the rectrices and tail, similar to adult but paler. First immature plumage resembles adults, but individuals retain a dark buff colouration on the throat, lores, forehead and crown, mixed grey and rusty brown on the chest, light buff on the flanks and belly, with white feathers emerging on the supercilium and malar region.

Taxonomy

The buff-sided robin was initially described under the binominal name Petroica cerviniventris (Family Petroicidae) by John Gould in 1857; however, placement in the genus Petroica was tentative. In a discussion relating to the buff-sided robin and closely allied white-browed robin, Gould subsequently observed that "...as both differ somewhat in form from the typical members of the genus, or true Petroica, it may in all probability be found necessary to institute a distinct genus for their reception". The buff-sided robin was later assigned to the genus Poecilodryas, a grouping that includes seven species from the Australian mainland, New Guinea, and the eastern Indonesian Islands of Misool, Salawai and Waigeo.<p>Gould recognised the similarity between the buff-sided robin and the closely allied white-browed robin (Poecilodryas superciliosa), a species discovered by John Gilbert in the Burdekin region of Queensland in 1845. Gould stated that the buff-sided and white-browed robin were "...doubtless representatives of each other in the respective countries they inhabit...". Between 1958 and 1994, a number of authors considered P. superciliosa (NE Australia) and P. cerviniventris (NW Australia) to be a single species as a result of these similarities.<p>Schodde and Mason reinstated Gould's original taxa P. superciliosa and P. cerviniventris as separate species on the basis of a comparison of all members of the superciliosa super-species, including the New Guinean black-sided robin (Poecilodryas hypoleuca). They found that P. cerviniventris showed distinct morphological and plumage variation when compared to P. superciliosa, including larger size, rich tawny-rufous flanks, white tipping on all rectrices, and duskier grey-brown upper dorsum. Schodde and Mason also note that there is no evidence of recent genetic flow between the two taxa across the Gulf of Carpentaria, and morphological differences are most extreme for populations that are closest in terms of distribution.<p>Subsequent genetic analysis indicates that while they are closely related, the two taxa display a degree of genetic divergence that is consistent with their recognition as separate species. Loynes et al. found that Poecilodryas is monophyletic and located within a clade, including Drymodes, Eopsaltria (excluding E. flaviventris), Tregellasia, Peneothello, Melanodryas, and Poecilodryas. All taxa within the clade (except Drymodes) are united in a strongly supported, monophyletic subfamily (Eopsaltriinae). Within the genus Poecilodryas, the Australian species P. cerviniventris and P. superciliosa are strongly supported as sister taxa, with Poecilodryas albispecularis as sister to this pair. Genetic similarity between P. superciliosa and P. cerviniventris is consistent with allopatric speciation as a result of geographic isolation of the two taxa on either side of the lower Gulf of Carpentaria.<p>The binominal name translates as stag-bellied dappled tree-nymph. The generic name Poecilodryas (from the Ancient Greek for 'spotted or dappled wood-nymph') refers to the spots on the wing and tail of species in this genus, and to its characteristic flight and perching behaviour. The specific epithet cerviniventris refers to the buff colouration of the chest, derived from Latin cervus = 'stag, deer' and ventris 'vent, belly'.

Scientific name

Poecilodryas cerviniventris

Authority

(Gould, 1858)

Order

Passeriformes

Family

Petroicidae

Genus

Poecilodryas

Range and habitat

The buff-sided robin occurs in suitable habitat within northern coastal drainage basins from the Kimberley region of north-west Western Australia, the Top End of the Northern Territory to the north-western Gulf of Carpentaria in Queensland. In Western Australia, the buff-sided robin occurs within the Central Kimberley, Northern Kimberley and Ord Victoria Plain IBRA Bioregions with scattered records from King Edward River, Prince Regent River, Wunaamin Miliwundi Ranges, Drysdale River/Kalumburu, Mitchell River, Mitchell Plateau, Fitzroy River, Geikie Gorge, Pentecost River, Wyndham and Kununurra. In the Northern Territory, the buff-sided robin occurs within the Victoria Bonaparte, Darwin Coastal, Arnhem Coast, Pine Creek, Daly Basin, Gulf Coastal, and Gulf Fall and Uplands IBRA Bioregions. In the western Northern Territory, the range of the buff-sided robin extends from the Western Australian border to Kakadu National Park within the Keep River, Victoria River, Fitzmaurice River, Moyle River, Daly River, Darwin River, Finniss River, Adelaide River, Mary River, Wildman River, West Alligator River and East Alligator River catchments. It is absent from eastern Arnhem Land, but occurs in eastern Northern Territory within the Roper River, Limmen Bight River, McArthur River, Robinson River, Calvert River and Settlement Creek drainage basins. In north-west Queensland, the buff-sided robin occurs in the Gulf Plains IBRA Bioregion, with all known records located within the Settlement Creek and Nicholson River drainage basins. Within these catchments, populations are known from the Gregory River, Nicholson River, Boodjamulla (Lawn Hill) National Park and Lagoon Creek (Westmoreland Gorge).<p>The buff-sided robin is largely confined to dense riparian vegetation, and subcoastal and sandstone monsoon vine-thickets. At riparian sites, it prefers thickets of freshwater mangrove, pandanus, and bamboo. The core riparian forest habitat of the buff-sided robin is characterised by canopy and sub-canopy trees, including Melaleuca leucadendra, Nauclea orientalis, Ficus, Terminalia, Pandanus aquaticus, and Barringtonia acutangula. Buff-sided robins are strongly associated with these dense, closed canopy, vegetation communities, rarely venturing into adjacent drier and more open forest types. Buff-sided robins have been reported occasionally from tidally influenced mangrove communities near the coast.<p>Observations of the habitat of the buff-sided robin were provided by Elsey, who described it as living in "mangroves" on the Victoria River, a reference to the freshwater mangrove (Barringtonia acutangula) that occurs on the lower banks of freshwater reaches of rivers in the region. Whitlock confirmed Elsey's habitat observations on the Victoria River, reporting that the buff-sided robin was "...one of the most attractive inhabitants of the river forests, to which it seemed to be almost exclusively confined", and that it "...favoured thickets of freshwater mangroves". Hill described the buff-sided robin on the McArthur River (Gulf of Carpentaria) as being "Found in thick scrub and timber in sheltered localities, generally near water". Barnard described it as "...common along the water-courses and in the brush growing at the foot of the sandstone bluffs" in the McArthur River catchment, the latter comment referring to dry monsoon vine-thickets associated with sandstone escarpments. At the eastern extremity of its range on the Gregory River (north-western Queensland), the buff-sided robin was reported by McClennan to occur in riverine habitat and "...when disturbed makes for the pandanus growing along the river-banks, where it is usually to be found at other times, and in which it doubtless nests."

Migration

Resident species

Behavior

Migration pattern: Resident species.

Conservation

Population trend: rising.

Population trend

rising