Ospreys were extinct in the UK for four decades before returning in the 1950s
Conservationists are attempting to lure rare ospreys to new nesting sites in southern England using polystyrene models of the birds in "show homes".
Osprey breeding grounds are centred on Scotland and the RSPB wants to see them spread to other parts of the country.
The charity hopes the birds will be tempted into thinking the new sites are good places for ospreys to settle as they return from the winter in Africa.
Five fake nests are at Arne reserve and two at Poole harbour, both Dorset.
The RSPB says ospreys would once have been widespread but became extinct in the UK for four decades before returning to breed in the 1950s, with the birds now mainly found in Scotland.
Mark Singleton, RSPB visitor manager at Arne, said: "This is a really exciting experiment and one that has worked at other locations in Europe, so we're hopeful that before long we might just have some breeding ospreys of our own."
He added: "If we did get ospreys breeding at Arne it would be an amazing conservation success story and, as well as improving the population and range of this magnificent bird a little more, it would be fantastic for all our visitors."
Two "polyospreys" have been to added to the 6ft-wide stick nests which have been splashed with white paint to give them that "lived-in" look.
The Dorset coast has been chosen because ospreys are adapted to catching fish.
The RSPB hopes from there they will spread to other parts of the south of England, which provides better food sources than their current home in Scotland.