Buff-sided robin

The buff-sided robin (Poecilodryas cerviniventris) is a small, diurnal, insectivorous, perching (passerine) bird in the family Petroicidae, a group commonly known as the Australo-Papuan or Australasian robins. It is also known as the buff-sided fly-robin, buff-sided shrike-robin and Isabellflankenschnäpper (German). The buff-sided robin is endemic to northern Australia, where it primarily occurs in riparian forests and monsoon vine thickets from the Kimberly region of Western Australia to the north-west Queensland Gulf of Carpentaria. The plumage of the adult birds is characterised by a dark hood and back with a prominent white stripe on the supercilium; a white throat, white wing and tail bars, and a striking buff to orange patch on the flank below the wings. Adult birds are not sexually dimorphic; however, males are generally larger and can be separated from females based on morphological measurements. Buff-sided robins predominantly take insects from the ground by sallying from an observational perch. Insect prey are also occasionally taken by hawking on the wing or by gleaning from the trunk or foliage of riparian vegetation.

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.

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).

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.

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.