By Victoria Gill
Science correspondent, BBC News
Britain's loudest bird, the "booming" bittern, is making a recovery after almost disappearing from the UK twice.
The RSPB reported the birds had had a "record-breaking year" in 2021, with 228 males counted, up from 209 in 2019.
Ornithologist Dr Alex Lees described it as a "spectacular conservation success story" thanks to the restoration of wetland habitats.
"It shows that conservation does work," the Manchester Metropolitan scientist told BBC News.
Bitterns, a member of the heron family, are well camouflaged wetland birds that hide in reed beds.
The best way for conservation scientists to count them is during the breeding season – by listening for the male's booming "foghorn" call, which can be heard three miles (5km) away.
Unlike other birds, the male bittern does not use its voice box but muscles around his windpipe to expand his entire gullet into an echo chamber.
The birds were driven to extinction across the UK in the 1870s.
A combination of hunting and draining of their wetland homes for agriculture led to their disappearance.
They returned to Britain in the early 20th Century but numbers were very low when the first annual surveys began in 1990.
And in 1997, there were estimated to be just 11 males across the whole of the UK, putting them on the brink of a second national extinction.
But systematic restoration and re-creation of wetlands over recent decades has allowed their numbers to more than double in the past 10 years, the RSPB says.
Simon Wotton, a senior conservation scientist from the wildlife charity, said: "[Their] recovery shows how quickly nature can bounce back when given the chance."
Dr Lees said the success of wetland conservation "isn't just about bitterns".
"We've invested millions in restoring and creating wetlands and that's meant species like cranes, spoonbills, little egrets and great egrets have returned too.
"Wetland birds are probably the biggest conservation success story of the last 40 years – it's the group of species that's really bucking the trend of nature loss."
Wetlands also play a role in flood protection and combatting climate change, by locking away carbon-rich plant matter in their mud.
So their restoration was a "win-win for wildlife and people", Mr Wooton said.
"We hope that one day the boom of the bittern will be heard around the UK once more."
Follow Victoria on Twitter .
Marshland 'engineered' to fight climate change
Does feeding garden birds do more harm than good?
Zelensky says Russia reeling from 'powerful blows'
Russia targets east Ukraine, says first phase over
Kim fronts Hollywood-style video to launch missile
Is Russia admitting invasion not going to plan?
Ros Atkins on… Putin’s false Nazi claims about Ukraine. Video
Will Ukraine invasion push Japan to go nuclear?
The women who paid the price of Ethiopia's civil war
Thousand-year-old oaks seed experimental 'super forest'
Celebration as the Oscars ceremony returns to Hollywood
The people and streets behind Branagh’s Belfast. Video
The surprising dark side of empathy
The priest shot at a checkpoint
The most powerful man you've never heard of
Searching for Vladislav Surkov, key architect of the 'post truth' world
It changed her life, now she wants answers
Zara McDermott investigates the impact of revenge porn
From eating crusts to hanging up horseshoes…
Why are superstitions and old wives' tales so trusted?
© 2022 BBC. The BBC is not responsible for the content of external sites. Read about our approach to external linking.
RSPB: Bitterns make booming recovery in UK wetlands – BBC
By Victoria Gill