Species Guide: Eurasian Bittern (Botaurus stellaris)
Family: Ardeidae
The Eurasian Bittern, also known as the Great Bittern, is a large, secretive heron-like bird found in reedbeds and marshes across temperate Europe and Asia, with small populations also present in North Africa. It is famous for its booming, bull-like call and exceptional camouflage; a stocky, heavily streaked bird built for hiding in tall reeds.
Appearance
Male
Males are generally slightly larger and more robust than females. They have a heavy, compact body; a short neck when folded; and a long, dagger-like bill. Plumage is warm buff to brown, streaked and barred with dark brown or black that breaks up the bird’s outline among reeds. In display (e.g., when booming), the throat and breast may appear puffed, aiding sound production.
Female
Females are similar in pattern and coloration to males but tend to be marginally smaller and sometimes a little paler or less boldly marked. Sexes are otherwise cryptic and hard to separate at a glance in the field without measurements.
Juvenile
Juveniles resemble adults but often show a warmer, more rufous cast and may have fresher, less-worn plumage with slightly different streaking. Young birds can appear a bit paler, and their barring may be less crisp than that of adults.
Diet
Eurasian Bitterns are opportunistic predators that forage in shallow water and along reed margins. Their diet is dominated by:
- Fish (including freshwater eels and small cyprinids), sometimes surprisingly large relative to body size.
- Amphibians (frogs and newts).
- Aquatic invertebrates (crustaceans, large insects).
- Small mammals (voles, mice) and occasionally small birds.
They hunt by standing or moving slowly with their head low, then spearing or grasping prey with their strong bill. Bitterns swallow fish head-first and may eat prey whole.
Habitat
Bitterns are specialists of well-developed reedbeds (often Phragmites) and large marshes with a mosaic of open shallow water and emergent vegetation. They prefer extensive reed systems (tens of hectares) where dense cover and shallow hunting zones provide both shelter and food. They will also use reed-fringed lakes, lagoons, slow rivers, and sometimes flooded agricultural fields, particularly outside the breeding season.
Summer
Resident
Winter
Behavior
General behavior
Eurasian Bitterns are largely crepuscular and secretive by day, remaining concealed within stems and vegetation. When disturbed, they often freeze with neck extended and bill pointed upward, relying on cryptic streaking to disappear among reeds. When they move, it is slow and deliberate; in flight, they show rounded wings and a heavy, direct wingbeat.
Call: “The boom”
The species is best known for the male’s deep, resonant “boom”. A low-frequency bellowing sound that carries across marshes in spring and early summer. The booming is produced by the male during display from a concealed perch and is used to advertise territory and attract mates. The sound has long inspired folklore, likened to a bull or a distant drum. Recordings and sonograms show long low notes and a characteristic reverb that can make the call audible for several kilometres in still conditions.
Life cycle
Movement: Some populations are resident, others are partially migratory. Northern breeders may move south in winter.
Breeding season: Spring–early summer (timing varies by latitude). Males begin booming in late winter to early spring.
Nesting: A platform nest of reeds is built low in the reedbed, usually supported by denser vegetation above shallow water.
Clutch & development: Females lay several eggs (typically 3–6). Incubation is mostly by the female and lasts about 23–26 days. Chicks are semi-precocial, downy, able to move a little soon after hatching but dependent on parents for food. Young fledge after several weeks but may remain in the territory while learning to feed.
Biometrics
There is geographic and individual variation, eastern forms may show bolder barring and some size differences. These figures represent commonly cited averages from field guides and research summaries.
| Length | 70-80 cm |
| Wing Span | 125-135 cm |
| Body Weight | 0.9-1.5kg grams |
| Longevity | 4 Years |
Natural Predators
Adult Eurasian Bitterns have relatively few predators due to their size and secretive reedbed lifestyle, but threats include:
- Large birds of prey (e.g., marsh harriers) that may take fledglings or occasionally adults in open conditions.
- Mammalian predators (e.g., foxes, mink, feral cats) that can raid nests and catch chicks or eggs, especially where reedbeds are fragmented or accessible.
- Egg and chick predation by corvids or gulls if nests are exposed.
Habitat structure (deep water, dense reeds) is the primary natural defense against predation.
Relationship to Humans
Bitterns have long been part of human folklore and culture across Europe and Asia. Their booming call, mysterious presence, and reedbed habitat produced many local names (e.g., “bull of the bog”, “mire drum”, “boom bird”) and myths. Ancient writers including Pliny, attached fanciful origins to their Latin name (Botaurus), likening the boom to a bull’s bellow. Local fables often emphasize the bird’s secretive nature; stories sometimes portrayed it as an omen or as a small creature with a surprisingly mighty voice.
Humans have affected bitterns both negatively and positively:
Positive actions: Active reedbed restoration, water-level management, and targeted conservation programs have produced local recoveries (see Conservation section). The species acts as a flagship for reedbed conservation and wetland restoration because its presence indicates a healthy, functioning marsh ecosystem.
Negative impacts: Historical destruction and drainage of wetlands, reed cutting at the wrong time, pollution, overfishing, and invasive species have reduced suitable habitat in many areas. Nest disturbance and fragmentation increase vulnerability to predation.
Conservation Status
Global status: The Eurasian Bittern is currently assessed as Least Concern on the IUCN Red List, with a broad range and a large total population. The global population trend is generally considered stable overall, although regional trends vary.
Regional trends & threats: While some core areas show stable or recovering populations, other regions experienced declines in the 20th century due to wetland loss, pollution, and reedbed degradation. Local declines can be pronounced where wetlands have been drained or where water management prevents the shallow margins they require. Conservation success is strongly tied to habitat management (maintaining water levels, reed cutting rotation, controlling pollution, and preventing reedbed fragmentation).
Examples of recovery: The United Kingdom provides a clear conservation success story: decades of reedbed restoration and careful water management have increased breeding populations. Recent monitoring reported a record year for booming males in the UK (e.g., surveys showing increases and local recoveries), demonstrating that targeted habitat work can produce tangible results. Nevertheless, the species remains dependent on continued wetland protection and appropriate management.
U.K.
Conservation Status
Global
Conservation Status
Ad Space
References
- Lovette, I. et al. (2016) The Cornell Lab of Ornithology, handbook of bird biology. Third edition. Chichester: Wiley. [Accessed 15/10/2025]
CITATIONS
- By Cephas – Own work, CC BY-SA 3.0, [Accessed 09/11/2025] ↩︎
