Great bittern
The Eurasian bittern or great bittern (Botaurus stellaris) is a wading bird found in parts of Europe, across the Palearctic, and in Africa. It is a secretive bird, seldom seen in the open as it prefers to skulk in reed beds and thick vegetation near water bodies. Its presence is apparent in the spring when the booming call of the male during the breeding season can be heard.
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CrepuscularCrepuscular animals are those that are active primarily during twilight (that is, the periods of dawn and dusk). This is distinguished from diurnal...
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CarnivoreA carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of a...
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OviparousOviparous animals are female animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive...
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Soaring birdsSoaring birds can maintain flight without wing flapping, using rising air currents. Many gliding birds are able to "lock" their extended wings by m...
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SemiaquaticSemiaquatic animals are those that are primarily or partly terrestrial but that spend a large amount of time swimming or otherwise occupied in wate...
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Wading birdsWading birds forage along shorelines and mudflats searching for small aquatic prey crawling or burrowing in the mud and sand. These birds live in w...
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PolygynyPolygyny is a mating system in which one male lives and mates with multiple females but each female only mates with a single male.
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Partial MigrantPartial migration is when within a migratory species or even within a single population, some individuals migrate while others do not.
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starts withThe Eurasian bittern is the largest of the bitterns, with males being rather larger than females. The bird has a black crown and nape, with the individual feathers rather long and loosely arranged, tipped with buff and narrowly barred with black. The sides of the head and neck are a more uniform tawny-buff, 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 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 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 on the feet. Juveniles have similar plumage to adults but are somewhat paler with less distinct markings.
Eurasian bitterns breed across temperate parts of Europe and Asia from the British Isles, Sweden, and Finland eastwards to Sakhalin Island in eastern Siberia, Korea, and Hokkaido Island in Japan. The 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. Some populations are sedentary and stay in the same areas throughout the year. More northerly populations usually migrate to warmer regions. Eurasian bitterns inhabit reed beds, swamps, lakes, lagoons, and sluggish rivers fringed by rank vegetation. They sometimes nest by ponds in agricultural areas. Outside the breeding season, they frequently visit rice fields, watercress beds, fish farms, gravel pits, sewage works, ditches, flooded areas, and marshes.
Eurasian bitterns usually spend time singly, foraging in reed beds. They walk stealthily or remain still above a body of water where prey may occur. They are shy birds, and if disturbed, often point their bill directly upwards and freeze in that position; their cryptic plumage blends into the surrounding reeds, and the birds become almost unspotted - this behavior is known as 'bitterning'. Eurasian bitterns are very secretive in nature, trying to always stay hidden in the reeds and coarse vegetation. Occasionally, especially in hard winter weather, they stand in the open beside the water's edge, although usually close to cover. They seldom fly, however, except when feeding young, prefer to move through the vegetation stealthily on foot. Their gait is slow and deliberate and they can clamber over reeds by gripping several at a time with their toes. Eurasian bitterns are most active at dawn and dusk, but also sometimes forage by day. The mating call or contact call of the male is a deep, sighing fog-horn or bull-like boom with a quick rise and only slightly longer fall, easily audible from a distance of 5 km (3 miles) on a calm night.
Eurasian bitterns are carnivores. Their diet includes fish, small mammals, amphibians, and invertebrates. They eat eels up to 35 cm (14 in) and other fish, mice, voles, small birds and fledglings, frogs, newts, crabs, shrimps, mollusks, spiders, and insects. In continental Europe, members of over twenty families of beetle are eaten, as well as dragonflies, bees, grasshoppers, and earwigs. Eurasian bitterns also add to their diet some aquatic plants.
Eurasian bitterns are polygynous, with males mating with up to five females. The mating season takes place between January and April. Bitterns build their nests in the previous year's standing reeds. The nest is an untidy platform some 30 cm (12 in) across. It may be on a tussock surrounded by water or on matted roots close to the water and is built by the female using bits of reed, sedges, and grass stalks, with a lining of finer fragments. The female lays 4 to 6 eggs in late March and April and incubates them 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 into the nest from her crop. The chicks become fully fledged at about 8 weeks and reach reproductive maturity at one year of age.
The main threat Eurasian bitterns face is the destruction of reed beds and drainage and the disturbance of their wetland habitats. The southern race has suffered a catastrophic decline during the 20th century due to wetland degradation and, unlike the northern race, is of high conservation concern.
According to the IUCN Red List, the total population size of the Eurasian bittern is around 115,000-340,000 individuals. The European population consists of 75,300-133,000 mature individuals. Currently, this species is classified as Least Concern (LC) on the IUCN Red List, but its numbers today are decreasing.
