Habitat

• Fertile peat bogs with extensive sedge cover near river valley floodlands

Sites with medium and large sedge tussocks, sometimes mixed with Molinia caerulea and short, sparse reeds (Phragmites australis). Sparsely scattered, small bushes, which often constitute the males' singing posts, are a regular feature of this habitat. This type of habitat is more or less associated with agriculture (burning or mowing of meadows).

• Mesotrophic or slightly eutrophic sedge peat bogs

The principle flora consists of short and medium-sized tussock-forming or erect sedges situated in shallow water (1-10 cm/0,25 – 4 in.). Aquatic Warbler avoids habitats with cottongrass (Eriophorum) and peat moss, and areas where the water is too deep, bushes are too dense and tall or where sedge tussocks are too tall. From an analysis of the location of 92 Aquatic Warbler nests recorded between 1995 and 1997, none were found in areas where the water level was higher than 20 cm (8 in.)

• Cladietum marisci with Cladium mariscus

Here the entire population occurs in Cladium mariscus rush.

• Periodically flooded  halophitic communities of the Baltic coast

The principle flora consists of short (80-120 cm/30-47 in.) and sparse reed. Aquatic Warblers have only been found in areas where reed density exceeds 100 stems/square meter. Basically, only areas with young, early succession reed are inhabited. In Polish Pomeranian sites commercial reed cutting provides this type of young reed habitat.

• Marshy meadows covered with tall grasses (Alopecurus pratensis and Phalaris arundinacea) and tussock sedge