Exhibits a slender, compact morphology characteristic of its genus, with a total length of 16 to 18 centimeters and a body weight ranging between 23 and 31 grams. Its dorsal plumage is predominantly dark grayish-brown, while the ventral region is visibly lighter. A subtle but distinct whitish supercilium extends behind the eye, contrasting with its darker crown. The throat displays a white background with fine dusky speckling. The breast and belly are a dull grayish-brown, showing distinctive grayish flanks that give this taxon its common name. In flight, it reveals an indistinct ochre or rufous wing stripe. Its bill is relatively short, thin, slightly decurved, and blackish in color, uniquely adapted for probing rocky substrates.
Geographical distribution: Occurs throughout the southern cone of South America, spanning a wide latitudinal range. It is found continuously in Chile, from the Atacama region south to Tierra del Fuego, and in western Argentina, covering Andean provinces from Mendoza southward through Neuquén, Río Negro, Chubut, and Santa Cruz. During the non-breeding winter season, some populations undertake migratory movements northward and eastward, with vagrant records documented in the Falkland Islands and along the Atlantic coast of Patagonia.
Habitat: Inhabits a diverse range of environments closely associated with freshwater bodies and rocky landscapes. It is commonly found near turbulent mountain streams, open gravel slopes, shrubby steppes, and rocky intertidal shores. Its altitudinal distribution is highly adaptable, ranging from sea level in the southern canals up to elevations of 3,000 to 4,000 meters in the central and northern Andes.
Feeding: Maintains an insectivorous diet consisting almost entirely of small invertebrates. It feeds heavily on aquatic and terrestrial insects, larvae, small crustaceans, mollusks, and spiders. It actively forages by walking on wet rocks, muddy shorelines, and kelp deposits on marine beaches, using its specialized bill to probe crevices and flip small stones.
Behavior: Characterized as a highly active, terrestrial bird that is mostly solitary or seen in pairs during the breeding season. It displays a typical tail-bobbing behavior accompanied by rapid wing-flicks when perched on rocks. Its flight is low, direct, and undulating, staying close to the ground or water surface. The species performs altitudinal migrations, moving down to lower valleys and coastal beaches during the harsh winter months of the Southern Hemisphere.
Nesting: Breeding activity occurs primarily between September and January. It constructs its nest at the end of a tunnel excavated in dirt banks, inside natural rock crevices, or within cavities in stone walls. The nest is a cup-shaped structure lined with dry grasses, soft plant fibers, and feathers. The clutch usually contains 2 to 3 white eggs. Both parents cooperate in incubating the eggs and feeding the altricial nestlings.
Conservation status: Categorized as Least Concern (LC) by the International Union for Conservation of Nature (IUCN). Although its global population is considered stable and faces no immediate threats of extinction, localized degradation of Andean aquatic ecosystems and the presence of invasive predatory species could impact local populations.
Compilation and publication: EcoRegistros – 25/08/2026