For a bird that prefers to remain elusive to the eye, ensconced among the dense cover of reedbeds, the bittern is far less inconspicuous to the ear. 

This rare and shy heron is a master of camouflage with plumage that perfectly blends into the reeds in which it hides, yet its booming call can be heard up to three miles away! 

It’s the territorial male bitterns that produce the big and mournful booming noise, which has been described as sounding like a distant foghorn, or a mooing cow, or even like someone blowing over the top of a bottle (except much louder). 

The birds’ distinctive call can be heard as early as January – often following mild and wet winters – and can continue into July, however, the best time to listen out for booming bitterns is between March and May. 

Bitterns themselves were once on the verge of local extinction in Britain. As recently as 1997, there were just 11 males remaining. 

However, the hard work of UK conservation bodies (with a lot of help from the EU and extra funding) has brought bitterns back from the brink. 

A study in 2017 estimated there to be an incredible 164 males booming from their reedbed homes.  

Interestingly, unlike most birds, bitterns do not use their voice box (or ‘syrinx’), and instead allow the muscles around their wind pipe (oesophagus) to strengthen and expand, turning their gullet into a great echo chamber that eventually makes up a phenomenal one fifth of his total body weight!  

If you’re heading out to hear a bittern, make sure to pick a still day when sounds can carry further, and then settle into a bird hide, keep your fingers crossed… and wait.  

Don’t worry, with the reedbeds alive with singing warblers, squealing water rails, pinging bearded tits and even the chance of a passing otter, it’s highly unlikely you will get bored! 

Attracting a mate is one of the key reasons why a male bittern will boom. Males will mate with up to five females each season, who will each produce four or five eggs in March or April. 

One of the best places in our region to experience a bittern’s boom is Fishlake Meadows Nature Reserve in Romsey. 

It’s worth familiarising yourself with the sound of the boom first, so you know what to listen out for.  

Check out this video on Hampshire & Isle of Wight Wildlife Trust’s website for some inspiration: hiwwt.org.uk/wildlife-explorer/birds/herons-egrets-spoonbill-and-crane/bittern