Bittern
The Bittern, Eurasian Bittern or Great Bittern is a bird in the bittern sub-family of the heron family.
Its folk names, often local, include many variations on the themes of "barrel-maker", "bog-bull", "bog hen", "bog-trotter", "bog-bumper", "mire drum(ble)", "butter bump", "bitter bum", "bog blutter", "bog drum", "boom bird", "bottle-bump", "bull of the bog", "bull of the mire", "bumpy cors" and "heather blutter". Most of these were onomatopoeic colloquial names for the bird. The call was described as "bumping" or "booming" and mire and bog denoted the bird's habitat.
As its alternative name of Great Bittern suggests, the Bittern is the largest of the bitterns with males being slightly larger than females. It is 27 to 32 inches in length with a 39 to 51 inches wingspan.
The crown and nape are black with the individual feathers rather long and loosely arranged and tipped with buff narrowly barred with black. The sides of the head and neck are a more uniform tawny-buff and irregularly barred with black. The mantle, scapulars and back are of a similar colour but are more heavily barred, the individual feathers having black centres and barring. The head has a yellowish-buff superciliary stripe and a brownish-black moustachial stripe. The sides of the neck are a rusty-brown with faint barring. The chin and throat are buff, the central feathers on the throat having longitudinal stripes of rusty-brown. The breast and belly are yellowish-buff with broad stripes of brown at the side and narrow stripes in the centre. The tail is rusty-buff with black streaks in the centre and black mottling near the edge. The wings are pale rusty-brown and irregularly barred, streaked and mottled with black. The plumage has a loose texture and elongated feathers on the crown, neck and breast can be erected.
The powerful bill is greenish-yellow with a darker tip to the upper mandible. The eye has a yellow iris and is surrounded by a ring of greenish or bluish bare skin. The legs and feet are greenish, with some yellow on the tarsal joint and yellow soles to the feet. Juveniles have similar plumage to adults but are somewhat paler with less distinct markings.
The mating call or contact call of the male Bittern is a deep, fog-horn or bull-like boom with a quick rise and an only slightly longer fall, easily audible from a distance of 3 miles on a calm night. The call is mainly given between January and April during the mating season. Surveys of Bitterns are carried out by noting the number of distinct male booms in a given area. Prior to modern science, it was unknown how such a small bird produced a call so low-pitched. Common explanations suggested that the bird made its call into a straw or that it blew directly into the water. It is now known that the sound is produced by expelling air from the oesophagus with the aid of powerful muscles surrounding it.
Usually solitary, the Bittern forages in reed beds by walking stealthily or remaining still above a body of water where prey may occur. It is a shy bird and if it is disturbed it will often point its bill directly upwards and freezes in that position, causing its cryptic plumage to blend into the surrounding reeds.
The Bittern has a secretive nature and keeps largely hidden in reeds and coarse vegetation. Occasionally, especially in hard winter weather, it will stand in the open beside the water's edge, although usually close to cover to facilitate a hasty retreat.
In flight, the Bittern’s 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 and prefers 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.
The breeding range of the Bittern extends across temperate parts of Europe and Asia from the UK, Sweden and Finland eastwards to Sakhalin Island in eastern Siberia and Hokkaido Island in Japan. The northern limit of its range is in the Ural Mountains and eastern Siberia whilst the southern limit is the Mediterranean Sea, the Black Sea, Iran, Afghanistan, Kazakhstan, Mongolia and northern China. Small resident populations also breed in Morocco, Algeria and Tunisia.
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, north and central Africa and northern Asian birds migrate to parts of the Arabian peninsula, the Indian sub-continent and eastern China.
In the UK, the Bittern can be found all year round at suitable wetlands, particularly in East Anglia, south east England and south west England. It is most visible in winter. In recent years, the Bittern has become a regular winter visitor to the London Wetland Centre, enabling city residents to view this scare bird.
The Bittern is typically found in reed beds 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 it prefers large reed beds of at least 50 acres in which to breed. Outside the breeding season it has less restrictive habitat requirements and, in addition to reed beds, it can also be found in rice fields, watercress beds, fish farms, gravel pits, sewage works, ditches, flooded areas and marshes.
Males are polygamous and mate with up to 5 females. The nest is built in the previous year's standing reeds and consists of an untidy platform some 12 inches across. It may be on a tussock surrounded by water or on matted roots close to water and it is built by the female using bits of reed, sedges and grass stalks with a lining of finer fragments. The clutch of 4 to 6 eggs is laid in late March and April and incubated by the female for about 26 days. After hatching, the chicks spend about 2 weeks in the nest before leaving to swim amongst the reeds. The female rears them without help from the male, regurgitating food from her crop. The chicks become fully fledged at about 8 weeks.
The Bittern feeds on fish, small mammals, amphibians and invertebrates, hunting along the reed margins in shallow water. Some vegetable matter such as aquatic plants is also consumed.
The Bittern has a very wide range and a large total population and therefore the IUCN has assessed its overall conservation status as being of "Least Concern” because although the population trend is downward, the rate of decline is insufficient to justify rating it in a more threatened category. The chief threat that the Bittern faces is the drainage and disturbance of its wetland habitats.
Date: 7th May 2018
Location: Ham Wall RSPB reserve, Somerset
Its folk names, often local, include many variations on the themes of "barrel-maker", "bog-bull", "bog hen", "bog-trotter", "bog-bumper", "mire drum(ble)", "butter bump", "bitter bum", "bog blutter", "bog drum", "boom bird", "bottle-bump", "bull of the bog", "bull of the mire", "bumpy cors" and "heather blutter". Most of these were onomatopoeic colloquial names for the bird. The call was described as "bumping" or "booming" and mire and bog denoted the bird's habitat.
As its alternative name of Great Bittern suggests, the Bittern is the largest of the bitterns with males being slightly larger than females. It is 27 to 32 inches in length with a 39 to 51 inches wingspan.
The crown and nape are black with the individual feathers rather long and loosely arranged and tipped with buff narrowly barred with black. The sides of the head and neck are a more uniform tawny-buff and irregularly barred with black. The mantle, scapulars and back are of a similar colour but are more heavily barred, the individual feathers having black centres and barring. The head has a yellowish-buff superciliary stripe and a brownish-black moustachial stripe. The sides of the neck are a rusty-brown with faint barring. The chin and throat are buff, the central feathers on the throat having longitudinal stripes of rusty-brown. The breast and belly are yellowish-buff with broad stripes of brown at the side and narrow stripes in the centre. The tail is rusty-buff with black streaks in the centre and black mottling near the edge. The wings are pale rusty-brown and irregularly barred, streaked and mottled with black. The plumage has a loose texture and elongated feathers on the crown, neck and breast can be erected.
The powerful bill is greenish-yellow with a darker tip to the upper mandible. The eye has a yellow iris and is surrounded by a ring of greenish or bluish bare skin. The legs and feet are greenish, with some yellow on the tarsal joint and yellow soles to the feet. Juveniles have similar plumage to adults but are somewhat paler with less distinct markings.
The mating call or contact call of the male Bittern is a deep, fog-horn or bull-like boom with a quick rise and an only slightly longer fall, easily audible from a distance of 3 miles on a calm night. The call is mainly given between January and April during the mating season. Surveys of Bitterns are carried out by noting the number of distinct male booms in a given area. Prior to modern science, it was unknown how such a small bird produced a call so low-pitched. Common explanations suggested that the bird made its call into a straw or that it blew directly into the water. It is now known that the sound is produced by expelling air from the oesophagus with the aid of powerful muscles surrounding it.
Usually solitary, the Bittern forages in reed beds by walking stealthily or remaining still above a body of water where prey may occur. It is a shy bird and if it is disturbed it will often point its bill directly upwards and freezes in that position, causing its cryptic plumage to blend into the surrounding reeds.
The Bittern has a secretive nature and keeps largely hidden in reeds and coarse vegetation. Occasionally, especially in hard winter weather, it will stand in the open beside the water's edge, although usually close to cover to facilitate a hasty retreat.
In flight, the Bittern’s 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 and prefers 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.
The breeding range of the Bittern extends across temperate parts of Europe and Asia from the UK, Sweden and Finland eastwards to Sakhalin Island in eastern Siberia and Hokkaido Island in Japan. The northern limit of its range is in the Ural Mountains and eastern Siberia whilst the southern limit is the Mediterranean Sea, the Black Sea, Iran, Afghanistan, Kazakhstan, Mongolia and northern China. Small resident populations also breed in Morocco, Algeria and Tunisia.
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, north and central Africa and northern Asian birds migrate to parts of the Arabian peninsula, the Indian sub-continent and eastern China.
In the UK, the Bittern can be found all year round at suitable wetlands, particularly in East Anglia, south east England and south west England. It is most visible in winter. In recent years, the Bittern has become a regular winter visitor to the London Wetland Centre, enabling city residents to view this scare bird.
The Bittern is typically found in reed beds 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 it prefers large reed beds of at least 50 acres in which to breed. Outside the breeding season it has less restrictive habitat requirements and, in addition to reed beds, it can also be found in rice fields, watercress beds, fish farms, gravel pits, sewage works, ditches, flooded areas and marshes.
Males are polygamous and mate with up to 5 females. The nest is built in the previous year's standing reeds and consists of an untidy platform some 12 inches across. It may be on a tussock surrounded by water or on matted roots close to water and it is built by the female using bits of reed, sedges and grass stalks with a lining of finer fragments. The clutch of 4 to 6 eggs is laid in late March and April and incubated by the female for about 26 days. After hatching, the chicks spend about 2 weeks in the nest before leaving to swim amongst the reeds. The female rears them without help from the male, regurgitating food from her crop. The chicks become fully fledged at about 8 weeks.
The Bittern feeds on fish, small mammals, amphibians and invertebrates, hunting along the reed margins in shallow water. Some vegetable matter such as aquatic plants is also consumed.
The Bittern has a very wide range and a large total population and therefore the IUCN has assessed its overall conservation status as being of "Least Concern” because although the population trend is downward, the rate of decline is insufficient to justify rating it in a more threatened category. The chief threat that the Bittern faces is the drainage and disturbance of its wetland habitats.
Date: 7th May 2018
Location: Ham Wall RSPB reserve, Somerset
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Also in: Herons and egrets
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