Inhabits grassland in swamps and flood plains. Grassbirds spend most of their time under cover, hopping and running while searching for insects. They are mostly sedentary but move nomadically to new, more suitable, areas.
Breeding takes place from August to April. During breeding, males advertise their territory with display flights with wings quivering and tail down, singing continuously then hovering before dropping down to return to cover. The nest is cup-shaped, narrower at the top, built of dried swamp grass and lined with finer grasses and rootlets. Built near the ground in dense cover such as grass clump.
Usually three, sometimes two, eggs are laid; they are pink, freckled with purple-brown and grey markings; long-oval in shape, about 20 millimetres by 15 millimetres.
Found along the northern parts of Australia from the Kimberley, to York Peninsula and down the eastern side of the continent to the Illawarra in New South Wales. Found in a coastal band reaching up to 300 kilometres inland (range includes the Warrambungle Ranges in New South Wales). Overseas distribution includes New Guinea to Timor and the Philippines. There are 15 or more races overall but only one race in Australia.
Common names include Tawny Marshbird, Rufous-capped Grassbird, Rufous-capped Grass Warbler.