It could be days before the true scale of the pollution spill affecting sea birds on the south coast of England is known, wildlife experts have said.
Conservationists believe many birds covered in a mystery sticky substance could have been blown out to sea by prevailing winds - leading to yet more fatalities as they are unable to feed and become cold and exhausted.
Hundreds of sea birds have died and hundreds more have been washed up on the coast between West Sussex and Cornwall after being covered in the pollutant. The RSPB said that just a handful of guillemots were recovered alive on Sunday from Chesil beach in Dorset and from Dawlish and Teignmouth in Devon. A similar amount of birds were found washed up dead.
Grahame Madge, of the RSPB, said: "The number of birds recovered today is very small but we don't think that reflects the absolute position. We really think it is a reflection of the prevailing weather conditions rather than the situation affecting sea birds.
"The winds on Friday were encouraging birds to come into the shore where they could be picked up but the wind since has been pushing birds more out to sea. It is quite likely that there has been many, many more birds affected who have no hope of rescue at the moment."
Mr Madge said that bird watchers on Chesil beach had spotted what they believed were many sea birds covered in the pollutant and in difficulty. He said: "We had bird watchers at Chesil beach reporting a large number of sea birds off shore that appeared to be struggling and never made it, as far as we can tell, to land.
"I think we are due westerly winds which means the birds could be pushed eastwards and that did seem to be what was happening in the last 48 hours with sightings reported in Hampshire and Sussex. It is quite often this way with spills or any pollution incident that we only expect to recover a small proportion of the total number of birds affected. It will depend entirely on the weather."
Mr Madge said the scientists were still trying to identify exactly what the pollutant was. On Friday, tests revealed the mystery substance as a refined mineral oil, but not from an animal or vegetable-based oil. They also ruled out palm oil. One expert said the oil could have been discharged into the sea accidentally or deliberately from a ship.
More than 250 birds, mostly guillemots and about 17 razorbills, are now being treated at the RSPCA West Hatch centre near Taunton, Somerset.
Peter Venn, manager of the centre, said: "It is still early days and hard to say how the birds will survive in the long-term. We don't know what this substance is or what it might be doing to the birds, but we can say the margarine does seem to remove it and we are doing all we possibly can to give them the best chance we can of survival."