Eurasian Bittern

Usually solitary, the Eurasian bittern forages in reed beds, walking stealthily or remaining still above a body of water where prey may occur. It is a shy bird, and if disturbed, often points its bill directly upwards and freezes in that position, causing its cryptic plumage to blend into the surrounding reeds, an action known as bitterning. While in this position, the shield of elongated feathers on throat and breast droop downwards and hide the neck, so that the outline of the head and body is obscured. Sometimes it resorts to applying powder down produced by patches of specialist down feathers at the side of its breast. This white dusty material seems to help it to rid its head and neck of slime after feeding on eels. It then removes the excess powder by scratching vigorously before applying preen oil from the gland at the base of its tail. The bird has a secretive nature, keeping largely hidden in the reeds and coarse vegetation. Occasionally, especially in hard winter weather, it stands in the open beside the water's edge, although usually close to cover to facilitate a hasty retreat. In flight, its wings can be seen to be broad and rounded, and its legs trail behind it in typical heron fashion. Its neck is extended when it takes off, but is retracted when it has picked up speed. It seldom flies however, except when feeding young, preferring to move through the vegetation stealthily on foot. Its gait is slow and deliberate and it can clamber over reeds by gripping several at a time with its toes. It is most active at dawn and dusk, but also sometimes forages by day. Eurasian bitterns feed on fish, small mammals, amphibians and invertebrates, hunting along the reed margins in shallow water. British records include eels up to 35 cm (14 in) and other fish, mice and voles, small birds and fledglings, frogs, newts, crabs, shrimps, molluscs, spiders and insects. In continental Europe, members of over twenty families of beetle are eaten, as well as dragonflies, bees, grasshoppers and earwigs. Some vegetable matter such as aquatic plants is also consumed. Males are polygamous, mating with up to five females. The nest is built in the previous year's standing reeds and consists of an untidy platform some 30 cm (12 in) across. It may be on a tussock surrounded by water or on matted roots close to water and is built by the female using bits of reed, sedges and grass stalks, with a lining of finer fragments. The eggs average 52 by 38 mm (2.0 by 1.5 in) and are non-glossy, olive-brown, with some darker speckling at the broader end. Four to six eggs are laid in late March and April and incubated by the female for about twenty-six days. After hatching, the chicks spend about two weeks in the nest before leaving to swim amongst the reeds. The female rears them without help from the male, regurgitating food into the nest from her crop, the young seizing her bill and pulling it down. They become fully fledged at about eight weeks.

The breeding range of B. s. stellaris extends across temperate parts of Europe and Asia from the British Isles, Sweden and Finland eastwards to Sakhalin Island in eastern Siberia and Hokkaido Island in Japan. The bird's northern extent of occurrence is around 57°N in the Ural Mountains and 64°N in eastern Siberia. Its southern limit is the Mediterranean Sea, the Black Sea, Iran, Afghanistan, Kazakhstan, Mongolia and Hebei Province in northern China. Small resident populations also breed in Morocco, Algeria and Tunisia. It typically inhabits reed beds (Phragmites) and swamps, as well as lakes, lagoons and sluggish rivers fringed by rank vegetation. It sometimes nests by ponds in agricultural areas, and even quite near habitations where suitable habitat exists, but for preference, chooses large reed beds of at least 20 hectares (49 acres) in which to breed. Some populations are sedentary and stay in the same areas throughout the year. More northerly populations usually migrate to warmer regions but some birds often remain; birds in northern Europe tend to move south and west to southern Europe, northern and central Africa, and northern Asian birds migrate to parts of the Arabian peninsula, the Indian sub-continent, and the provinces of Heilongjiang, Jilin and Inner Mongolia in eastern China. Outside the breeding season it has less restrictive habitat requirements, and as well as living in reed beds, it visits rice fields, watercress beds, fish farms, gravel pits, sewage works, ditches, flooded areas and marshes. The subspecies B. s. capensis is endemic to southern Africa, where it is found sparingly in marshes near the east coast, the Okavango Delta and the upland foothills of the Drakensberg Mountains. This population is sedentary.

Not globally threatened.