A wetland reserve famous for the thousands of swans which visit every winter is opening a new 38 hectare (94 acre) wildlife habitat.
The extension to the Wildfowl and Wetlands Trust's (WWT) Welney Reserve, called Lady Fen, has been converted from farmland to wet grassland.
It is a joint project between the Environment Agency and WWT.
The Environment Agency bought the land to make up for wildfowl habitat lost to flood defence work.
The work was carried out by the Environment Agency on the middle level barrier bank of the Ouse Washes from 2001 to 2005.
The bank was eroded by waves from the Washes over time, and new concrete panels were installed along some stretches.
While the work stabilised the area it meant some habitat for over-wintering wildfowl was lost.
Lady Fen was created by digging a system of ditches, channels and scrapes.
The ground has been seeded with native grasses and a waterproof liner has been inserted to protect the surrounding farmland.
Wildfowl such as wigeon feed on short grass over the winter.
Leigh Marshall, WWT's reserve manager, said: "We are delighted that our partnership with the Environment Agency has worked so well in providing this extra wildlife habitat.
"Lady Fen has already attracted hundreds of wigeon, golden plover and other wildlife."