ONE of the UK's rarest birds - with a stronghold in East Anglia - is thought to have had its best breeding season in at least 130 years.

David Green

ONE of the UK's rarest birds - with a stronghold in East Anglia - is thought to have had its best breeding season in at least 130 years.

Seventy five male bitterns have been counted in their reedbed habitats all over the country this year - a 47% increase on last year and nearly seven times as many as recorded in 1997 when the bittern was on the verge of extinction.

East Anglia remains the bird's stronghold with 24 males - known as boomers because of their distinctive cry - counted along the Suffolk coast, including eleven at Minsmere, which remains the most important individual site.

Twenty one “boomers” were recorded in the Norfolk and Suffolk Broads with four on the north Norfolk coast and 12 in the Fens, including two in the RSPB's relatively new Lakenheath Fen reserve, created to help compensate for coastal losses due to sea level rise.

However, conservationists are still hoping more birds will colonise inland sites because 80% of the bittern population is in coastal areas vulnerable to habitat loss through sea level rise and increase in tidal surges.

Male bitterns, each of which has a slightly different “boom”, are used to gauge the size of the bittern population because the females have no call. The total UK population of the birds - including both sexes - may be around 130-140 and it is confined to the English counties.

Only eleven booming males were detected in the UK in 1997, the lowest point since detailed records began, but the creation of new reedbeds and the restoration of those which had been under-managed has resulted in a resurgence.

Dr Mark Avery, the RSPB's conservation director, said: “The bittern has suffered an ill-fated history in the UK, having endured extinction once and having been on the verge of extinction again in the late 1990s.

“We weren't prepared to accept a second extinction of the bittern, so we launched a rescue bid which has been so successful that a wide range of other wildlife has benefited too. There are too many threatened species in the world and the turning around of the UK's bittern population shows what can be achieved with a combination of practical determination, proper research and appropriate funding,” Dr Avery said.

Researchers believe this year's bumper population is directly linked to the very wet winter, which provided ideal feeding conditions for female bitterns, allowing them to get into breeding condition.

Ian Barthorpe, the RSPB's Minsmere spokesman, said about 80% of the population relied on habitats vulnerable to the impact of climate change. “It will be a healthier situation when more birds breed inland and reliance on Minsmere and other vulnerable coastal sites is reduced,” he said.

Dr Pete Brotherton, head of biodiversity for Natural England, said: “This year's figures are a fantastic achievement and show that we can bring species back from the brink of extinction. You would probably have to go back at least 130 years to find a better year for this booming bird.”