The distinctive boom of the 'Bittern' is becoming more common, with record numbers heard this year.
The RSPB says the bird has flourished despite a drier than average winter and loss of habitat due to some coastal flooding.
Bitterns are highly secretive wetland birds and live most of their time within dense stands of reed, making them very difficult to survey.
However, scientists count bitterns by listening for the male's foghorn-like booming call, which can reach more than 100 Decibels in volume.
In the UK the RSPB recorded 164 'booming' males this year, 8 of those were at Lakenheath Fen.
Nearly half of the UK bitterns breed within Special Protection Areas designated under the EU Birds Directive.