By Alex Kirby
BBC News Online environment correspondent
One of the UK's rarest birds, the bittern, can look forward to a more secure future.
Back from the brink: Bitterns could boom again (Image: Andy Hay/RSPB Images)
Conservationists hope work to improve the reedbeds where they live will double the numbers of bitterns within a decade.
In 1997 the population was so small there were fears the bittern could become extinct.
The European Union is paying more than half the cost of the rescue plan.
Eight conservation groups are working on the plan, including the Royal Society for the Protection of Birds (RSPB) and three county wildlife trusts.
The European Union's Life-Nature programme, the only EU funding dedicated to promoting nature conservation, is providing 60% of the £4m cost.
Bitterns are similar to herons, and grow to 30 inches (76 centimetres) in maturity.
They used to be relatively well established in the UK, but since the 1950s have been in growing trouble, mainly because of the decline of the reedbeds where these secretive birds like to live.
The surviving reedbeds became smaller and more fragmented and therefore unattractive to bitterns, which do not like to nest in areas smaller than about 50 acres (20 hectares).
By 1997, the bitterns appeared to be on the way out. Sarah Alsbury is the manager of the rescue project.
Vanishing reedbeds were the bittern's downfall
She said: "When nesting, bitterns need large reedbeds with areas of open shallow water. By 1997, conservationists feared they were on the edge in Britain, when only 11 calling males were noted in just four counties."
The project hopes to expand the bittern's range by creating seven new reedbeds, enlarging five smaller ones, restoring three dry reedbeds and increasing the potential of four that currently host bitterns.
This strategic network of 19 sites will stretch from Kent and Suffolk in eastern England to Cornwall in the far west and Lancashire in the north.
The project builds on a successful four-year emergency EU scheme begun in 1996 which averted the threat of extinction in the UK.
Work at one site, Minsmere in Suffolk, has involved raising the water table and lowering the reedbed.
This makes it easier for the bitterns to fish in the reeds, not in open water, which they avoid.
Bittern camouflage is effective (Image: Andy Hay/RSPB Images)
They prefer eels or rudd, 19,000 of which are being introduced at Minsmere.
So far this year about 40 male bitterns have been recorded in several places across the UK, the highest number since 1983.
But it is still only half the number recorded in the 1950s, and the project hopes to double the present bittern population within 10 years.
The number of birds is estimated from the booming sound made by the males to announce their territory and attract females.
The sound is said to be like that made by blowing across the top of an empty milk bottle. Each bird has its own distinctive voice.
Bitterns are bigamists, with one male having up to five mates. Rivals are stabbed to death.
When food is short they become cannibals, eating the smallest bird in a brood.