Adult Male Upperparts green-brown, with black feather centres obvious on back and tertials, and with fine white marbling, streaks, or spots overall. Uniform green-brown wing-coverts with many white flecks. Blue-grey on supercilium, cheeks, and throat, and black patch between eye and bill. Grey foreneck, with faint spots. Olive-brown chest tinged grey. Barred black and white flanks continuing onto under wing and over vent, isolating bright buff under tail-coverts. Flight-feathers dark brown, with leading edge of longest primary white. Underwing grey-black, barred white. Female Face less grey with more spotting than male and underparts less grey with more spotting. Adult bare parts Bill yellow or yellow-green, base orange-yellow with base orange-yellow or orange-red. Juvenile Like female but face and breast lack any grey tone more buff-brown with little spotting. Bill black or dark brown becoming paler during the autumn from yellow-brown with dusky tip.

A bird of shallow sedge fens, its call (a whip like 'hooid') can be heard as much as 2 km away, and is delivered in bursts at a rate of up to 90 a minute.  

Most records for VC55 have been in the autumn between August and October with a three spring records up to 2013.

It is primarily a summer breeder to the Western Palaearctic, although there are some winter records, particularly in southern countries. Most winter North Africa and further south. It is a scare breeder in the UK and is not easy to prove breeding due to its secretive nature.

Migrant breeder and passage visitor.

Rare vagrant, mostly in autumn.