Breeding between October and December, Cobb’s wren lays three or four eggs per clutch in a dome-shaped nest built by the male of grasses, with an entrance hole near the top (1) (3) (4) (8) (9). The nest is lined with the soft feathers of several bird species, and is well hidden in tussac grass or in a rock crevice (3) (4), between ground level and 60 centimetres above the ground (5). It is possible that a breeding pair will produce two clutches a year. Cobb’s wren is tame and disregards human presence if it does not feel threatened, often feeding near them (2).
Cobb’s wren feeds on invertebrates found within dead kelp on beaches, within tussac grass, and under or around boulders (2) (8). Although often difficult to see, Cobb’s wren will reveal its presence through song, a mixed phrase of rapid trills, whistles and harsh notes, used to defend territories and attract mates during the breeding season (9) (10). Males on Carcass Island have been shown to live for at least six years, and probably stay in the same territory for life (4) (10).