Bittern
Botaurus stellaris (Linnaeus, 1758)
BI
BITTE
950
Family: Pelecaniformes > Ardeidae
Seeing a Bittern is always difficult, owing to their preference for dense reedbeds and to their strongly cryptic plumage, but they are famous for the far-carrying, booming call of the male in spring.
British Bitterns breed in our largest and least disturbed reedbeds, most often in nature reserves, where they benefit from well-directed conservation efforts and carefully designed habitat creation. When on migration, and in winter, they also occur in smaller and more open wetlands, though still preferring dense cover.
Sonagram analysis of Bittern calls has helped the monitoring of breeding numbers by allowing researchers to identify males individually, while radio-tracking has identified which elements of a reedbed environment are conducive to successful nesting. Conservation interventions have enabled Bitterns to increase their breeding numbers in Britain around tenfold since 2000.
Identification
Bittern identification is usually straightforward.
SONGS AND CALLS
Listen to example recordings of the main vocalisations of Bittern, provided by xeno-canto contributors.
Flight call
Song
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Population size and trends and patterns of distribution based on BTO surveys and atlases with data collected by BTO volunteers.
CONSERVATION STATUS
This species can be found on the following statutory and conservation listings and schedules.
POPULATION CHANGE
Previously widespread, Bitterns becamee extinct in the UK in the late nineteenth century before returning and increasing to around 80 booming males in the 1950s (Brown et al. 2012). The number of Bitterns in the UK then declined to a low of 11 booming males in 1997 (Brown et al. 2012) but has subsequently increased and has been rising consistently over the last ten years, with a new record total of 227 pairs counted in 2019 (Eaton et al. 2021). The breeding range has consequently also expanded considerably over the 40 years since the 1968–72 Breeding Atlas (Balmer et al. 2013).
DISTRIBUTION
The extensive wet reedbeds that Bitterns require for breeding are provided at clusters of sites in Kent, East Anglia, Somerset and Yorkshire. In winter, Bitterns are much more widespread and can be found at many smaller sites with a mix of reedbeds and pools and also along riverbanks.
Occupied 10-km squares in UK
No. occupied in breeding season | 82 |
% occupied in breeding season | 2.7 |
No. occupied in winter | 497 |
% occupied in winter | 16 |
European Distribution Map
DISTRIBUTION CHANGE
A few areas along the Norfolk and Suffolk coastline, in the Norfolk Broads and in north Kent have recorded breeding Bitterns in all three breeding atlases. Recent gains at inland sites correspond with extensive habitat creation schemes.
Change in occupied 10-km squares in the UK
% change in range in breeding season (1968–72 to 2008–11) | +134.3% |
% change in range in winter (1981–84 to 2007–11) | +157.4% |
SEASONALITY
Bitterns are recorded throughout the year, but most often in winter and in spring when its territorial booming calls can be heard, and when adults may be seen on provisioning flights.
Movement
Information about movement and migration based on online bird portals (e.g. BirdTrack), Ringing schemes and tracking studies.
RINGING RECOVERIES
View a summary of recoveries in the Online Ringing Report.
Foreign locations of birds ringed or recovered in Britain & Ireland
Biology
Lifecycle and body size information about Bittern, including statistics on nesting, eggs and lifespan based on BTO ringing and nest recording data.
SURVIVAL & LONGEVITY
View number ringed each year in the Online Ringing Report
Maximum Age from Ringing | 11 years 11 months 16 days (set in 2012) |
Typical Lifespan | 4 years with breeding typically at 1 year |
Adult Survival | 0.7±0.05 |
CODES & CLASSIFICATION
Ring size | J |
Field Codes | 2-letter: BI | 5-letter code: BITTE | Euring: 950 |
For information in another language (where available) click on a linked name
Research
Interpretation and scientific publications about Bittern from BTO scientists.
CAUSES AND SOLUTIONS
Causes of change
Degradation of habitat was considered an important driver of the declines between the 1950s and the late 1990s, with water levels within reedbeds being important (Tyler et al. 1998, Brown et al. 2012). Bitterns require extensive reedbeds for breeding and the recent increases have been driven by conservation efforts which have led to existing reedbeds being restored and new sites being created. Ongoing management of habitat is likely to remain important especially in the face of likely effects of climate change in south-east England (Brown et al. 2012).
Links to more studies from ConservationEvidence.com
- Nest box provision to provide additional nesting sites for bearded tits Panurus biarmicus at Leighton Moss RSPB Reserve, Lancashire, England
- Introduction of water buffalo Bubalus bubalis to recently created wetlands at Kingfishers Bridge, Cambridgeshire, England
- Introduction of rudd Scardinius erythropthalmus as food for bitterns Botaurus stellaris at Titchwell Marsh RSPB reserve, Norfolk, England
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