Barred warbler  (Sylvia nisoria)

Classified as Least Concern (LC) on the IUCN Red List (1).

The largest member of the genus Sylvia, the curious-looking barred warbler has a stout, pointed bill used to probe crevices for prey and a long tail that acts as a balance as the bird weaves its way through dense vegetation (2) (3). This plain-plumaged warbler has brownish-grey upperparts, sometimes with a slight tinge of blue, and distinctive greyish-barred, whitish underparts (2) (4). The crown, ear-coverts and scaled tail are noticeably darker, with a white edge around the outermost tail feathers. The bill and legs are dark grey (2) (4). The male and female birds are similar in appearance, although the female tends to have more uniform brownish upperparts and less barred underparts. The barred warbler is an extremely vocal bird and typically produces a vigorous, yet musical warble of short phrases, as well as various rattles and harsher notes (2).

The migratory barred warbler has a large breeding range that extends from Central Europe through Central Asia to western China and south-eastern Mongolia. Outside of the breeding season, all populations travel southwards to East Africa, with birds mainly gathering in Kenya, as well as southern Sudan, eastern Uganda, northern Tanzania, and possibly also Chad (2).

The barred warbler is mainly a forest species, requiring the presence of trees or bushes up to three metres tall, but it is also found in a variety of open wooded habitats with thorny bushes, isolated trees and a rich undergrowth. In Africa it occurs in dry open woodland dominated by Acacia trees. The barred warbler is also found around hedgerows, parks, plantations, meadows and pasture, usually at altitudes below 1,600 metres (2).

The barred warbler has a highly complex and unusual method of breeding. From May to July, territorial males attract female mates with songs, wing-clapping in flight, and by building a loose nest platform, the quality of which is believed to indicate the male bird’s health. After a pair have bonded, the female uses the material from this platform to help build a more elaborate cup-shaped nest in a dense thorny bush. Once the pair have mated, the female lays a clutch of three to six eggs and the male bird may abandon the female to take-up a new territory, in attempt to mate with additional females. Some males, however, choose to stay with the original female and form a monogamous relationship. When this is the case, both birds share incubation duties for around 12 or 13 days, and both tend to the chicks while they are in the nest for a further 11 or 12 days. After fledging from the nest, the young birds remain with the adults for around three weeks. When the adult male bird has more than one mate, the female incubates the eggs and tends to the chicks alone. Sexual maturity is reached at around one year, although most barred warblers do not breed until their third year (2).

The barred warbler feeds largely on insects, which are usually plucked off leaves in bushes near the ground, or in the canopy of tall trees, on the ground or in flight (2). It is this dependency on insect prey that explains why the barred warbler must migrate southwards after breeding; during the winter at northern latitudes insects become scarce, but at this time insects are in abundance in the tropics. The barred warbler typically leaves its breeding grounds in July, arriving at the wintering grounds around December, where it remains until around March or April (2). Before the barred warbler embarks on its long journey, it accumulates substantial fat reserves which act as an energy store (3).

The barred warbler has a very large population, and is therefore not thought to be under any threat of extinction (5) (6). There are also no known major threats to the species. The population does, however, fluctuate quite substantially, most likely because of changes in the weather in the East African part of its range. One breeding population in the eastern Baltic is thought to have gone extinct as a result of an extremely dry period in the species’ wintering grounds (7). 

In the absence of any major threats to the barred warbler’s survival, it has not been the target of any known conservation measures (1).

Environment Agency - Abu Dhabi is a principal sponsor of ARKive. EAD is working to protect and conserve the environment as well as promoting sustainable development in the Emirate of Abu Dhabi.

View information on this species at the UNEP World Conservation Monitoring Centre.

To find out more about the conservation of birds, see:

• BirdLife International:
  http://www.birdlife.org/
• Royal Society for the Protection of Birds:
  http://www.rspb.org.uk/