Length: 64 – 81 cm
Wingspan: 100 – 130 cm
Weight: 865 – 1940 g
Adult bitterns have golden-brown upperparts with golden patches and black streaks. The primaries and tail are reddish-orange with black speckles and streaks. There are some elongated feathers on the back of the neck and shoulders which they can erect.
The upperparts are paler with vertical dark streaks and the breast, belly, and flanks are streaked with reddish-brown. The throat is pale golden-brown.
They have a black crown and nape and a dark moustachial stripe that starts at the base of the bill and extends down to the sides of the head. The lores vary according to season becoming blue in the males during breeding season.
The long, pointed bill is yellow-green, the eyes are yellow or orange, and the legs and feet are green. Both sexes are similar.
Juvenile bitterns resemble the adults with streaks on the crown and moustache. They are less marked on the mantle and scapulars, and have paler wing coverts.
Bitterns breed from early March to May. The female builds the nest in reedbeds which is a floating platform constructed from dry reeds and aquatic plants and lined with finer materials. It is secured with stems to the reedbed.
Bitterns lay 4-6 greenish-brown eggs with brown spots which are incubated by the female alone for 26 days. Chicks are altricial and covered with reddish-brown down. They are fed by the female with regurgitated food. They leave the nest at about 12 days into the surrounding vegetation. At 8 weeks they have full plumage and are able to fly. They reach sexual maturity at a year.
Bitterns eat a varied diet of fish, amphibians and insects. They have also been known to eat small mammals and in some parts of Europe eels form a principal part of their diet.
Where to see them
Bitterns are found in wetlands with large reedbeds. They are most visible during the winter.
Did you know?
A bittern’s boom, emitted by males during breeding season, can be heard up to 2 km away.