Some of the 988 birds collected by the RSPCA from the oil spilled from the MSC Napoli could be released back into the wild by the end of this month.

The sick birds have been picked up along a coastal stretch from Torbay in Devon to Kimmeridge in Dorset in the two weeks since the damaged container ship was grounded near Sidmouth in Devon. They are all guillemots apart from 12 razorbills, a great northern diver and two shags. Hundreds more birds have washed up dead on the shoreline.

Staff at RSPCA wildlife centres across the country have been cleaning the birds and doing everything they can to help them to survive.

Each bird's health is continually assessed and monitored and it is hoped that some of the strongest and healthiest guillemots could be released within four weeks.

Sadly, guillemots' survival rates after being covered in oil are low, although the RSPCA is constantly searching for ways to improve their future chances. The birds affected by the Napoli spill will, for example, be released near shoals of sprat - one of the guillemot's favourite food - which will be located using sonar.

However, research suggests that only 40 per cent of the oiled guillemots will survive long enough to be released back into the wild. Furthermore, previous studies have shown that only about one per cent live for more than a year following release.

Tim Thomas, a senior scientific officer in the RSPCA's wildlife department, said: "It's very sad, but the survival rates of the oiled guillemots is known to be extremely poor, so we are trying everything we can to give them a better chance of survival.

"Being covered in oil like this is life-threatening. It stops them being able to fly or dive for food. It also reduces their buoyancy. By the time they are washed up on the beach they may be less than two-thirds their original weight and suffering from extreme exhaustion after paddling a long way. Many more birds than those we are caring for may have died out to sea."

Cleaning the birds is a long and time-consuming process, which has stretched the resources of the charity's wildlife centres. It may be months before some of the birds are strong enough to be released.

The birds, which are often dangerously underweight and cold when they come into RSPCA care, are weighed and checked for burns - mostly caused when the oil gets mixed with other contaminants. Their stomachs are flushed with a solution containing activated charcoal to rehydrate them and reduce the amount of poison they absorb from any oil they may have swallowed. Coloured rings as well as British Trust for Ornithology rings are put around their legs to enable them to be identified following release.

Cleaning is a labour-intensive process which takes two people up to 15 minutes per bird. They are then put in a warm drying room overnight. Blood samples are taken to check for illnesses and poisons from the oil. They are also fed sprats in an attempt to increase their weight.

Healthy birds declared fit by vets are given a second, more detailed clean. There follows a period where their physical fitness is assessed in deep outside pools. After a final assessment they are released in areas that closely match their normal migratory patterns to allow them to get back to their breeding colonies.

What to do if you find oiled birds: Do not risk your safety by looking for or picking up birds from dangerous locations. Be aware of the tides and weather conditions.

If you do find an oiled bird and it is safe to pick it up, ensure that you are wearing gloves because the oil could be hazardous to your health. The birds may bite too.

Collected birds should be placed on their own in cardboard boxes with newspapers or towels. DO NOT use hay or straw.

Call the RSPCA 24 hour helpline 0870 5555 999 which can arrange collection or inform you of a nearby collection point. Alternatively you can take the birds directly to the RSPCA West Hatch Wildlife Centre near Taunton, Somerset.

Do not attempt to wash or feed the birds - leave that to the experts.