Bittern – Botaurus stellaria

Only present in winter in Wiltshire, the Bittern can be very hard to spot; yet the booming voice of the male can be heard in late winter across dense reed-beds and marshy areas. A good spot to try and see Bitterns in winter is at the Wiltshire Wildlife Trust’s Langford Lakes Nature Reserve.

Habitat

Lives in swamps and marshes spending most of its time in thick waterside vegetation. The best reed-beds are those that are shallow with reeds of different ages, along with channels and deeper areas of water for hunting fish.

Description

A thickset heron, the Bittern’s plumage is subtly mottled in various shades of brown, which help it to blend with the reed stalks amongst which it lives.

Upperparts are golden brown above, mottled and barred with black. Underparts are yellow-buff, striped with reddish-brown, barred and spotted with black. They have a black crown and moustache and the feathers on the neck are thicker and elongated. The bill is long and pointed, almost dagger-like, and a dark yellow tinged with green in colour.

Biology

More likely to be heard rather than seen, the Bitterns loud booming call, made by the males in the breeding season, can be heard from up to two kilometres under suitable conditions. Male Bitterns begin to boom as early as late January to establish territories and attract mates.

Some males are polygamous, and occasionally several nests, each built by a different female, are found within the territory of one calling male. There is no pair-bond as such, and the male normally takes no part in nest building or raising the young.

Nests are built in last years standing reeds in which four to five eggs are laid in March – April, there is usually only one brood per year. The female incubates the eggs, and after hatching, the chicks spend about two weeks in the nest and then disperse amongst the reeds. Not much is known about the chicks feeding or behaviour once they have left the nest.

It is a secretive bird that, when startled, adopts a camouflage posture of its bill pointed upwards and neck stretched vertically helping it to blend into its surroundings. Chicks adopt this camouflage posture when they leave the nest.

Their diet consists of fish, in particular eel, amphibians and invertebrates which they quietly hunt along the reed margins in shallow water and on the edges of dykes.

Threats

Habitat loss has been the biggest threat to Bitterns. Reed beds have gone under a massive decline due to lack of management, drying out, loss to agriculture and pollution. Some coastal sites around the UK have been lost due to sea level rise where the salt water kills of the reed beds and also the food sources on which the birds depend. Its dependence on reed beds and very small population make it a Red List species - one of the most threatened in the UK.

Conservation

The Bittern is protected under Schedule 1 of the Wildlife and Countryside Act (1981), which affords special protection at all times. It is an offence to take, injure or kill a Bittern or to take, damage or destroy its nest, eggs or young. It is also an offence to intentionally or recklessly disturb the birds at, or close to, their nest during the breeding season.

It is also included in the Birds of Conservation Concern Red List - (UK). As part of the UK Biodiversity Action Plan (UKBAP) Natural England has produced an action plan for reed bed birds in England as well as individual Species Action Plans (SAPs) for the Bittern. It is also included in Natural England’s Species Recovery Programme, which aims to restore existing reed beds back to favourable condition and to create new reed bed habitats both close to and away from traditional bittern breeding grounds.