This mysterious bird can be heard from 5 kilometers away, and the call sound it makes is extraordinary

Amidst the serenity of a spring morning in the British wetlands, there is one particular noise that is eagerly awaited more than anything else. Resonant and metallic in its sound, it reverberates across the marshes like a foghorn from afar.

This incredible sound comes from one of Britain’s most secretive birds: the Eurasian bittern.

As reported by Discover Wildlife, the male bittern produces a low-frequency “boom” that can travel up to 5 km across reedbeds and wetlands. The call has often been compared to the noise made when blowing across the top of an empty glass bottle.

The mysterious “booming” bird
Botaurus stellaris, scientifically known as the Eurasian bittern, is a shy wetland bird from the heron family. The bird lives most of its life hidden among dense reedbeds. Because of its excellent camouflaging abilities, the bird is hardly visible; it is often heard rather than seen.

In addition, according to Birdfact, the bird can stand still with its bill pointed upward to blend into its surroundings if it feels threatened.

However, despite being such a secretive bird, the male Eurasian bittern loudly announces his presence during the breeding season.

The call is mainly used to find a mate and to drive other males away from its breeding areas. According to the RSPB, the bittern’s boom is considered one of the loudest bird calls in the UK and can carry for nearly three miles in spring conditions.

A sound heard before sunrise
Springtime is said to be the prime season for listening to bitterns in Britain. The reedbed reserves come alive before dawn, with the sounds of warblers, cuckoos, and other birds inhabiting the wetlands.

What sets the call of the bittern apart from the rest is its richness and intensity. Reportedly, bittern census counts in Britain involve counting “booming” males each May, largely because they are so difficult to locate.

Additionally, according to the reports, conservationists rely on such vocal surveys to monitor the species in England and Wales. However, bird experts say that calm conditions during the early mornings or evenings present the best opportunity to hear the sound reverberate in the wetlands.

From near-extinction to recovery
The booming sound was once on the verge of disappearing from Britain altogether. As stated, bitterns became extinct as a breeding species in Britain in the late nineteenth century due to hunting and habitat destruction. Although they returned later, their population fell sharply again by the 1990s.

The reports note that only 11 booming males were left by 1997. Nevertheless, many years of successful efforts in wetland recovery and reedbed protection yielded positive results. According to the most recent data released, there were 283 booming male bitterns in 2024, the largest number since counting started in 1990.

It showed a 20 per cent increase compared to the previous year. The rise was said to be a “spectacular comeback.”

A rare sight in Britain’s wetlands
Today, bitterns can be found in large reed beds within East Anglia, Somerset, Kent, and other wetland areas. Reportedly, although bittern numbers have recovered, the bird remains rare and elusive in Britain, hiding among the reeds while preying on fish and amphibians.

This secrecy makes hearing a male bittern’s call all the more rewarding.

Even before a glimpse of the bird is seen, its voice may be carried on the misty air as it rings out over the marshes, sounding much like something from days long gone by.