RSPB England’s, Beth Markey, delves into the history and behaviour of the bittern – a bird that has defied the odds and made its way back into the hearts and minds of bird lovers across the country.

Once numerous across our wetlands, bitterns have overcome enormous hurdles in a seemingly endless battle against extinction. From just 11 calling males in the 1990s to today’s soaring population of more than 200, the bittern has become an emblem of optimism in a growing fight for ecological survival.

The bittern owes its success to dogged determination from nature organisations (with generous funding from the EU-LIFE project) that have worked relentlessly to curb this species demise. But efforts don’t just stop at bitterns. Brand-new reedbed habitats, created to home and protect breeding bitterns, have had significant benefits for wetland species including water voles and the reed leopard moth.

For this alone, the bittern is well deserving of the Bird of the Decade crown.

About the bittern

  Photo credit: Ben Andrew

The timid bittern is a master of disguise. Dubbed ‘the loudest bird in Britain’, you’ve more likely heard a bittern’s booming call than seen one in the flesh.

Slinking silently amongst the reedbeds, bitterns remain cloaked from prying human eyes for most of the year, much in contrast to their gregarious cousin, the grey heron. But in spring, they shake off their secretive customs in search of mates, issuing rumbling booms that exceed more than 100 decibels in volume.

Although nowadays, the bittern’s hollow call is considered a rare treat, it could be heard in abundance prior to the late Victorian era. So plentiful were bitterns, that they merited themselves several local nicknames, including bog blutter, buttle, bumbagus, myre-dromble, miredrum, bog-bluiter and butterbump.

Sadly, habitat degradation, hunting and slow breeding growth caused this bird’s rapid decline, with the species going extinct in the UK at the end of the 19th Century and again, after a slow return, teetering on the brink of a second extinction much later in the 20th Century. The bitterns’ historical decline and specific conservation needs - well-managed reedbeds with easy access to fish - kept it on the UK’s red list for many years.

A group of bitterns is known as a sedge, pretence or a siege, although on the whole they are solitary creatures. Being quite new on the scene, scientists and conservationists are still exploring the behaviours of this reticent bird, and flocks have occasionally been observed.

A timeline

 Photo credit: Ben Andrew

  • 19th century and before – bitterns are a common wetland bird. Their popularity is referenced in literature stretching as far back as Chaucer’s The Wife of Bath’s Tale when the bittern, rather famously, ‘bombleth in the myre’.

  • Late 19th Century – bitterns go extinct in the UK, a victim of wetland drainage and hunting.

  • 1911 – bitterns are recorded breeding again in Norfolk. By 1954, an impressive 80 booming males are inhabiting the UK.

  • 1954 – 1997 – a lack of reedbed management causes bitterns to decline sharply again. By 1997, only 11 males are recorded in the UK, with a similar pattern of decline across Western Europe.

  • 1996 – 2000 – RSPB pioneers a large project funded by the EU-LIFE programme to restore bittern habitats and make them suitable across thirteen sites. The project works to raise water levels in reedbeds, control the growth of bushes, and excavate and reshape pools and ditches in the reedbeds.

  • 2004 – bittern numbers increase on ten of the thirteen project sites, with particular success at RSPB Minsmere, where population numbers rise from just two in 1997 to nine by 2004.

  • 2002 – 2006 RSPB works in conjunction with other organisations to drive its second EU-LIFE programme funded bittern project, this time aimed at developing a wider network of reedbeds suitable for breeding or wintering bitterns. The population is now at 55 booming male birds.

  • 2008 – bitterns return to Somerset for the first time in 40 years. Two nests are observed at RSPB Ham Wall nature reserve.

  • 2011 – more than 100 breeding males are recorded – a significant spike in the population from just five years before.

  • 2016 – growth in bittern numbers is significant - 162 over 78 sites. The birds’ booming is recorded at three new sites – two in Wales and one in the Ouse Washes, Cambridgeshire.

  • 2019 a minimum of 200 boomers are recorded at 90 sites, compared to 189 boomers at 83 sites in 2018. On RSPB reserves, 102 confirmed boomers are recorded, up from 92 in 2018.

  • 2020 and onwards – in-depth research, development and monitoring has stopped reedbed degradation and shaped high-quality conditions for bittern breeding. Prospects for bitterns are positive, although climate change poses a risk, with the potential for sea level rise to make coastal reedbeds uninhabitable for bitterns. New reedbed habitats inland, such as Lakenheath Fen in Suffolk, aim to mitigate this risk.


Where to see bitterns

 Photo credit: Ben Andrew

These days, you can find bitterns in plenty of sites across England, with the majority taking up residence in Somerset. 38 of Somerset’s 48 booming males can be found at RSP Ham Wall, Natural England’s Shapwick Heath and Somerset Wildlife Trust’s Westhay Moor. Bitterns can also be found at the Fens, on the Suffolk coast and the Norfolk Broads, to name some of the more populous areas.

The best time to visit is during the spring breeding season, although males can start booming as early as late January in a bid to establish territory. Bitterns can be found on the following RSPB reserves. Why not get in touch with your nearest reserve to find out more about your local ‘siege’?

The 2010s saw a wealth of fantastic birding moments. Tell us - what is your Bird of the Decade?

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