The 'once heard, never forgotten' call of a rare bird has been heard at an east London nature reserve for the very first time.
RSPB Rainham Marshes, located beside the Thames, recorded the booming call of a male bittern.
Bitterns have been seen at the reserve before, but this is the first time their distinctive sound has been confirmed at the reserve.
The bittern is known for its deep, resonant "booming" call, described as similar to blowing over the top of a milk bottle. The sound can travel up to three miles and is used by males to establish territory and attract mates during spring and summer.
Bitterns were declared extinct in the UK in the late 19th Century but made a small comeback, reaching around 80 booming males in the 1950s. However, numbers declined sharply again, dropping to just 11 in 1997.
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Karen Fiske, visitor experience manager at RSPB Rainham Marshes, said: "It's been wonderful to hear a bittern on our reserve for the first time and be able to introduce our visitors to its extraordinary sound. Once you have heard a bittern you never forget it!"
The bittern is a stocky, secretive member of the heron family, with pale buff-brown plumage and dark streaks. It moves quietly through reeds, hunting fish and staying out of sight.
Conservation efforts led by the RSPB and Natural England have driven a remarkable recovery.
The bittern depends on healthy reedbeds for feeding and breeding, so much of the conservation work has focused on restoring and creating these wetland habitats.
The bird's elusive behaviour makes visual surveys difficult. Instead, teams of volunteers and reserve staff listen for the birds’ booming calls to estimate population numbers each spring.
In 2025, a record 283 booming males were documented by the RSPB and Natural England, marking a 20 per cent increase from the previous survey. This is the largest year-on-year rise since monitoring began in 1990.
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