Bittern, feeding in reeds

Bittern

Alarmed by the plunging bittern numbers, the RSPB started a research programme to investigate the needs of this previously little-studied bird.

Bitterns in the UK

Bitterns are large birds which live in reedbeds and are more often heard than seen. 

In 2016, there were more than 160 booming males.

When we count the number of bitterns in an area, we do this by noting the number of birds that boom (the call the male birds use to attract a mate). This amazing booming sound can be heard from up to 5 kilometres away and each male’s boom is slightly different, so we can identify a male individually.   

Species status

  • Phase of recovery: Recovery
  • Amber list Bird of Conservation Concern

The drastic decline in bittern numbers

Once common in wetlands, bitterns became extinct as breeding birds in the UK in the late 19th century, as a result of wetland drainage and hunting. These birds were next recorded as breeding in Norfolk in 1911. They slowly recolonised from there and by 1954 there were around 80 booming males. 

However, numbers dropped again as their reedbed habitats became drier through lack of management. By 1997 only 11 booming bitterns were recorded in the UK and there was a similar pattern of decline in bitterns across western Europe.  

Back from the brink

Alarmed by the plunging bittern numbers, the RSPB started a research programme to investigate the needs of this previously little-studied bird. This led to some clear management recommendations that have been, and still are being, implemented at many sites in the UK. 

Bitterns are difficult to study as they are found at low densities in habitats which are difficult to work in. The research looked at the habitat that bitterns prefer, their feeding requirements, the home range of male bitterns, as well as female nesting requirements, chick diet and their dispersal. 

To find this information, lightweight radio-transmitters were attached to bitterns at two RSPB reserves so that their movements could be tracked. Later, young birds at the nest were also radio-tagged and their food preferences studied. 

Bittern Botaurus stellaris, gliding across a reed bed, Suffolk,

Continuing the improvement

The research results meant that we understood what bitterns needed so we could manage the habitat appropriately for them. Much of the work to make habitats more suitable has been carried out through two large RSPB-led projects funded by the EU-Life programme.

The first project, centred on East Anglia, was a partnership of seven organisations and ran from 1996– 2000 at thirteen sites. The project concentrated on restoring reedbeds by raising the water levels, controlling the growth of bushes, and excavating and reshaping pools and ditches in the reedbeds. By 2004, bittern numbers had increased at 10 of the 13 project sites. At the RSPB’s Minsmere nature reserve, two booming bitterns in 1997 had increased to nine by 2004. 

The second bittern project, from 2002–2006, was developing a wider network of reedbeds suitable for breeding or wintering bitterns. Eight organisations were involved at 19 sites. Much of the work involved creating seven square kilometres of new reedbeds. Improvements were alsomade to encourage more fish for the birds to eat, which increases the bitterns’ breeding success. By 2004, the UK bittern population had risen to a minimum of 55 booming male birds and the recovery has continued, with a total in 2016 of more than 160 booming males.

This was achieved because detailed RSPB research was rapidly put into practice, the conservation organisations managing reedbeds developed strong partnerships and because a high percentage of reedbeds in the UK are managed by conservation organisations.

Bittern Botaurus stellaris, adult, wading in reedbed at Lee Valley Country Park

The way ahead

Management work to date has stopped reedbed degradation, and the projects underway should provide significant areas of high-quality reedbed in the future. However, it will take many years for these new sites to mature.

The knowledge that the RSPB has gained about bitterns’ needs, as well as how to manage and create reedbeds, is being shared among those managing reedbeds. 

Overall, the prospects for UK bitterns appear to be good, though the population is at risk from climate change. As sea levels rise, saltwater could flow into coastal reedbeds, making the habitat unsuitable for bitterns.

As a result, several new reedbeds are being created inland, away from vulnerable coasts, such as Lakenheath Fen in Suffolk and the Hanson–RSPB Wetland Project in Cambridgeshire, where five square kilometres of reedbed are planned.

Acknowledgements

The research was undertaken as part of Action for Birds in England, a conservation partnership between English Nature and the RSPB. Key work was undertaken by partners within the two bittern projects funded by the EU-LIFE programme.

These include English Nature, The Broads Authority, The Wildlife Trusts, The Environment Agency, The National Trust and The Lee Valley Regional Park Authority.

Great bittern Botaurus stellaris, walking through reedbed habitat, RSPB Minsmere, Suffolk