Marsh harrier numbers have soared to a 200-year high in the UK, says the Royal Society for Protection of Birds.
The marsh harrier is found in Europe, Asia and Africa
The birds of prey, once extinct in the UK, have benefited from regeneration of their wetland habitat and a crackdown on pesticide use and persecution.
Between 1995 and 2005 breeding females increased by 131% from 156 to 360 while 800 young fledged in 2005, up from 350 for the same period.
From 1900 to 1920 the distinctive bird of prey was extinct in the UK.
Their demise started in the 1700s when their wetland habitat was drained for farmland.
Legal protection from game keepers and egg collectors led to a recovery in the 1950s before numbers declined again due to the use of pesticides such as DDT.
The chemicals led to toxic residues in the birds' prey which made their eggs easily crack, resulting in the only existing pair in 1971 being at the RSPB's Minsmere reserve in Suffolk.
Dr Mark Eaton, research biologist at the RSPB, said "It was a tragedy that also affected the peregrine falcon, buzzard and sparrowhawk, but we are pleased that the illegal killing of birds of prey is now much reduced in the English lowlands."
The bird of prey population has now recovered
The survey for the RSPB and English Nature shows the marsh harrier population has now recovered so much that they are spilling out of nature reserves and nesting in farmland.
The birds, also known as bald buzzards and the dun pickle, now breed in parts of Eastern England, Yorkshire, Lancashire and Scotland where they can be seen during spring and summer hunting for prey.
They can be spotted by their long tails and shallow V shaped wings which distinguishes them from other birds of prey.
Marsh harriers are known for spectacular courtship displays which involve male birds looping the loop and spinning through 360 degrees before releasing food in mid-flight to be caught by females who turn upside down to catch it in their talons.
Allan Drewitt, senior ornithologist for English Nature, said further increase in numbers was dependent on more habitat renewal and conservation.
"The marsh harrier is a stunning bird and we must continue working with farmers to protect birds nesting in crops and ensuring that nests are not destroyed during harvest," he said.