White-browed Treecreeper

The White-browed Treecreeper, Climacteris affinis, is the smallest member of the Australo-Papuan treecreepers, uniquely adapted to arid environments. This diminutive bird, measuring 14–16 cm in length with a wingspan of 22 cm and weighing a mere 21 grams, is a master of vertical ascents along tree trunks in its quest for invertebrate prey.

Identification Tips

Adult males are predominantly dark grey above, with a contrasting brown mantle and scapulars, and a black sub-terminal tail-band. Their faces are marked by black lores, a distinctive white tapered eyebrow, and streaked black and white ear-coverts. Below, they exhibit a grey upper breast and a lower breast, belly, flanks, and vent streaked with black and white. Females are similar but can be distinguished by a rufous stripe bordering the upper edge of the eyebrow and rufous-tinged streaking on the upper breast. Both sexes have a black bill, dark brown iris, and black legs and feet. Juveniles are paler with less distinct facial patterning.

Habitat

The White-browed Treecreeper is found in arid and semi-arid woodlands and shrublands across southern Australia, where it frequents Acacia, Casuarina, or Callitris species with varying understory densities.

Distribution

This species is sedentary, with two subspecies divided by the Spencer Gulf: C. a. affinis to the east and C. a. superciliosus to the west.

Behaviour

Pairs or groups defend large territories year-round, with an average size of 8.4 hectares in some regions. Their flight is characterized by undulating patterns, interspersed with brief flapping and long glides, revealing a buff wingbar.

Song & Calls

The White-browed Treecreeper's calls are a distinctive long 'prrrpt', reminiscent of an insect, contrasting with the short shrill 'peep' of the similar Brown Treecreeper.

Breeding

Breeding season varies geographically, starting as early as July in the west and August in the east, continuing until November. They may breed as simple pairs or in cooperative groups, with 'helpers' assisting in all aspects of nesting except incubation and brooding. Nests are shallow saucers in tree hollows, lined with soft materials. Females lay 1-3 speckled eggs, incubating them for 17–18 days, with fledglings remaining dependent for up to 37 days post-fledging.

Similar Species

The Brown Treecreeper (Climacteris picumnus) is similar but has duller breast streaks and confined ear-covert streaking. Their calls also differ significantly.

Diet and Feeding

The White-browed Treecreeper forages alone or in groups, employing a unique 'inching' climbing technique to extract ants and other invertebrates from bark and leaf litter.

Conservation status

Despite some population declines, the White-browed Treecreeper is classified as Least Concern globally. However, it faces threats from habitat loss and climate change, and is listed as Threatened in Victoria, Australia.