the rock wren (salpinctes obsoletus) is a small songbird of the wren family native to south america and western north america .
it is the only species in the genus salpinctes .
adults are about 12 cm long .
they have grey-brown upperparts with small black and white spots and pale grey underparts with a light brown rump .
additional distinctive features include a light grey line over the eye , a long slightly decurved thin bill , a long barred tail and dark legs .
they actively hunt on the ground , around and under objects , probing with their bill as their extraction tool .
they mainly eat insects and spiders .
its song is a trill that becomes more varied during the nesting season .
these birds are permanent residents in the south of their range , but northern populations migrate to warmer areas from the central united states and southwest canada southwards .
they are occasional vagrants in the eastern united states .
during the breeding season , they move to dry , rocky locations , including canyons , from southwestern canada south to costa rica to build cup nests in a crevice or cavity , usually among rocks .
