The Lesser Swamp Warbler or Cape Reed Warbler, Acrocephalus gracilirostris, is an Old World warbler

Old World warbler

The "Old World Warblers" is the name used to describe a large group of birds formerly grouped together in the bird family Sylviidae. The family held over 400 species in over 70 genera, and were the source of much taxonomic confusion. Two families were split out initially, the cisticolas into...

 in the genus Acrocephalus

Acrocephalus

The Acrocephalus warblers are small, insectivorous passerine birds belonging to the genus Acrocephalus. Formerly in the paraphyletic Old World warbler assemblage, they are now separated as the namesake of the marsh- and tree-warbler family Acrocephalidae...

. It is a resident breeder in Africa

Africa

Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

 from the Democratic Republic of the Congo

Democratic Republic of the Congo

The Democratic Republic of the Congo is a state located in Central Africa. It is the second largest country in Africa by area and the eleventh largest in the world...

, the Chad

Chad

Chad , officially known as the Republic of Chad, is a landlocked country in Central Africa. It is bordered by Libya to the north, Sudan to the east, the Central African Republic to the south, Cameroon and Nigeria to the southwest, and Niger to the west...

 and Ethiopia

Ethiopia

Ethiopia , officially known as the Federal Democratic Republic of Ethiopia, is a country located in the Horn of Africa. It is the second-most populous nation in Africa, with over 82 million inhabitants, and the tenth-largest by area, occupying 1,100,000 km2...

 south to South Africa

South Africa

The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

. This is a common species of reedbeds in standing water.

Description

The Lesser Swamp Warbler is a plain coloured smallish bird 14–16 cm long and weighing around 20 gm. Its upperparts are rich brown, and it has a white supercilium

Supercilium

The supercilium is a plumage feature found on the heads of some bird species. It is a stripe which runs from the base of the bird's beak above its eye, finishing somewhere towards the rear of the bird's head. Also known as an "eyebrow", it is distinct from the eyestripe, which is a line which runs...

. The underparts are white, with a rufous wash to the flanks. The long, strong bill has a slightly down-curved upper mandible; it is blackish-yellow with a yellower base. The legs are blue-grey and the eyes are brown. Adults of both sexes and juvenile birds are very similar in appearance,

The song is rich and melodious, a series of bubbly phrases that include trilling notes, cheerup chee trrreee and a large number of variations, with pauses between phrases.

Behaviour

The Lesser Swamp Warbler builds a deep, firm cup nest from strips of reed blades, grass and sedges, which is lined with finer grasses. It is always placed in reeds above water. It nests mainly from August to December, with the earliest nesters being those in the winter rainfall areas of the Western Cape Province

Cape Province

The Province of the Cape of Good Hope was a province in the Union of South Africa and subsequently the Republic of South Africa...

. It lays two or three brown eggs. This species is monogamous, pairing for life.

The Lesser Swamp Warbler is usually seen alone or in pairs, moving through wetland

Wetland

A wetland is an area of land whose soil is saturated with water either permanently or seasonally. Wetlands are categorised by their characteristic vegetation, which is adapted to these unique soil conditions....

 reedbeds, and clambering up and down reed stems. It eats insects and other small invertebrate

Invertebrate

An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...

s.

Conservation status

This common species has a large range, with an estimated extent of 5.700,000 km². The population size is believed to be large, and the species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (i.e. declining more than 30% in ten years or three generations). For these reasons, the species is evaluated as Least Concern.