The RSPCA, which is co-ordinating the operation said the move was necessary because its local treatment centres were unable to cope with the number of affected birds. They will be cleaned up at the organisation's centres in Guernsey and Jersey.
The first mercy flight laid on by Jersey European Airways took out 40 birds from Exeter Airport on Monday, with a similar number being transported yesterday and more expected tomorrow.
Colin Seddon, deputy manager of the RSPCA's wildlife hospital at West Hatch, Somerset, said: "It is very unusual for us to have to do this, but it is a massive problem which cannot be dealt with at this centre."
Currently 600 oiled seabirds are being treated at West Hatch, and another 300 were expected to arrive last night.
Conservationists are demanding a full public inquiry into the oil spill amid concern that commercial interests were put above the environment.
Much of the Pembrokeshire Coast National Park remains heavily polluted after the spill, with some wildlife rescue services predicting that the eventual death toll of seabirds could reach 50,000 in the worst environmental disaster since the Torrey Canyon wreck in 1967.
The Council for National Parks charity says the initial refusal to allow the damaged Sea Empress into Milford Haven may have been a crucial factor in subsequent pollution. It also fears thousands of tonnes of oil were forced out by pumping gas into the stricken ship during the salvage operation.
CNP director Amanda Nobbs has dismissed as inadequate the Government's proposed inquiry by Department of Transport marine accident investigators. She said: "A full and open public inquiry needs to establish whether the national park was sacrificed, and the extent to which those involved in the rescue were motivated to save the port and the ship above the national park coastline."
Fishermen, meanwhile, have agreed to maintain a voluntary ban on putting to sea while the clean-up operation along the South Wales coast continues. Nearly 300 fishermen and fish merchants held a crisis meeting in Milford Haven to set up an action group and draw up demands for compensation.
The Government is expected to announce an official fishing exclusion zone after studying reports from scientists.