Groups such as the RSPB and WWF say that if the Cardiff-Weston project went ahead, much of this vital feeding area that currently supports tens of thousands of migrating and wintering birds would be permanently submerged.

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The Ouse Washes includes a large floodplain which is looked after by the Royal Society for the Protection of Birds and provides a habitat for the Bewick's swan and whooper swan and wintering birds of prey, including the hen harrier, merlin, peregrine falcon and short-eared owl.

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The Royal Society for the Protection of Birds (RSPB) said it was worried about the potential impact to a wintering population of sea birds.

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