This is a medium-sized warbler. It is very similar in appearance to several other acrocephaline warblers, such as the reed warbler which also occurs in wetlands and has a similar breeding range. The male's distinctive song is useful for identification, as no other member of the genus mimics other birds to any significant extent. The species is monotypic, and there is no significant geographical variation. The sexes are alike in appearance.
Habitat and Distribution
The marsh warbler also tends to avoid the stands of pure reed which are the reed warbler's favoured habitat. It breeds in the middle latitudes of Europe and western Asia. The marsh warbler also tends to avoid the stands of pure reed which are the reed warbler's favoured habitat.
The marsh warbler is mostly insectivorous, also taking some spiders and small numbers of snails. It generally gleans insects from vegetation but sometimes catches them on the ground or in mid-air. In autumn small numbers of berries may be eaten.
The species is usually monogamous. Marsh warblers tend to choose new mates each year and do not necessarily return to breed in the same area as previous years. On their breeding grounds they are territorial, with territories often grouped into loose colonies. In Africa, they are essentially solitary, and may defend territories to some extent. The nest is a cup, made mostly from leaves and plant stems, and is usually in dense vegetation, at varying heights. Three to six eggs are laid. Both sexes bring food to the nestlings. In continental Europe at least, the species has a short breeding season, of 52?55 days. In some areas, such as Bulgaria, marsh warblers suffer significant levels of parasitism by common cuckoos.
Calls and Songs
The marsh warbler is best known for the highly imitative song uttered by males, and very occasionally by females. Each male marsh warbler incorporates imitations of a wide range of other birds into its song. Other passerines are most commonly imitated, but the calls of other kinds of bird such as waders, hornbills and pigeons have been noted too. On average, each male bird incorporates imitations of 75 other species into its song, with rather more African than northern species mimicked. All learning seems to take place in the summer the bird is hatched in Europe or Asia, and in its first winter in Africa. The calls of birds heard in subsequent years are not added to the warbler's repertoire. Females may utter a simple, non-imitative song, and a range of other calls are also known.