Acrocephalus paludicola (Vieillot, 1817)

Taxonomic Classification

The aquatic warbler, with the scientific name Acrocephalus paludicola, is an Old World warbler that belongs to the genus Acrocephalus.

Breeding Range and Population Estimate

It breeds in temperate eastern Europe and western Asia, and has an estimated global population of 11,000 to 15,000 breeding pairs.

Migratory Status

It is a migratory species that winters in west Africa.

Wintering Grounds

After many years of uncertainty, the main wintering grounds for much of the European population were finally discovered in Djoudj National Bird Sanctuary, Senegal, where between 5,000 and 10,000 aquatic warblers gather at this single site.

Migration Route and Passage Range

The species follows a south-westerly migration route, so it is regularly seen during its passage as far west as Great Britain and Ireland.

Habitat Requirements

This small passerine bird lives in wet sedge beds with vegetation shorter than 30 cm (12 in).

Population Decline and Stronghold

Habitat drainage has caused this species' population to decline, and 70% of the world's population now breeds in the Polesie region spanning eastern Poland and southern Belarus, which is the species' current stronghold.

Reproduction

The aquatic warbler lays 3 to 5 eggs in a nest built in low vegetation.

Mating System

The species is highly promiscuous, with most males and females producing offspring with multiple partners.

Size

It is a medium-sized warbler.

Adult Plumage and Morphology

Adult aquatic warblers have a heavily streaked brown back, pale underparts with variable streaking, a flattened forehead, and a strong, pointed bill.

Head Markings

They also have a prominent whitish supercilium and a distinct crown stripe.

Similar Species Distinction

The aquatic warbler can be confused with the juvenile sedge warbler, which may also display a crown stripe, but the aquatic warbler has stronger markings, and appears paler with a spiky-looking tail when in flight.

Sexual Dimorphism in Plumage

Like most warblers, the sexes of the aquatic warbler have identical plumage.

Juvenile Plumage

Unlike adults, young aquatic warblers have unstreaked breasts.

Diet

As with most warblers, the aquatic warbler is primarily insectivorous, but it will also eat other small food items, including berries.

Vocalization

Its song is a fast, chattering ja-ja-ja, interrupted by whistles that are typical of members of the genus Acrocephalus.

Genus Name Etymology

The genus name Acrocephalus comes from the Ancient Greek terms akros, meaning "highest", and kephale, meaning "head".

Genus Name Coining Context

It has been suggested that Naumann and Naumann believed akros meant "sharp-pointed" when they coined the name.

Specific Epithet Etymology

The specific epithet paludicola is from Latin, derived from paludis meaning "swamp" and colere meaning "to inhabit".