Reed warbler

The reed warbler (Acrocephalus scirpaceus) is similar in appearance to several other members of the warbler family, particularly the much rarer marsh warbler. It is one of the commonest European warblers, but it is not resident in the United Kingdom. It winters in Africa and is a summer visitor to Britain, where it breeds in reedbeds in East Anglia, along the south coast of England, and in similar environments in Wales.

  

Appearance

The reed warbler is about 12.5 centimetres long (5 inches). It has olive-brown upperparts and white to buff underparts. It has a longish bill and a rounded tail.

Behaviour

The reed warbler’s flight is low and jerky, with the tail spread out. It is most likely to be seen sidling up a reed stem one step at a time. It often climbs up the reeds to sing, grabbing hold of several for extra stability. However, as the reeds are unable to support a bird’s weight at the very top, the reed warbler may be hidden within the reeds when it sings. It is therefore more likely to be heard than seen.

The song is not particularly loud or high-pitched; indeed it has been described as “harsh and grumpy”.

Breeding

Reed warblers return to their nesting sites in late April or early May, the sites being reedbeds close to ponds, lakes and waterways such as the Norfolk Broads. The nest is woven around several strong reeds that anchor it in place. The reeds may or may not be directly over water; the reed warbler is not, after all, a water bird. The advantage of not being over water is that the nest is at less risk of being swamped by the wash from a passing boat that is going too fast. However, land-based predators such as mink or rats are more of a threat if the nest is more accessible from the landward side.

The nest is built from reed leaves and other vegetation and is shaped as a deep cup. This is protection against the eggs or young falling out of the nest should the reeds be disturbed by strong winds or waves.

Four or five eggs are laid in May or June, with both partners incubating them for 11-12 days, sometimes longer. The adults also take turns to feed the nestlings, for up to 14 days in the nest and as long again after they have fledged. Food consists of insects, larvae, spiders and small molluscs. Adult birds also eat berries.

Reed warbler parents are noticeably protective of their young, using their bodies to shield them from heavy rain and the heat of a strong sun. A second brood may be raised before the reed warblers leave for their winter quarters in September or October.

© John Welford