About 20 birds have been rescued from an oil spill at a picnic spot.
A swan, a glebe and 15 mallard ducks were plucked from the River Purwell in Hitchin, Hertfordshire, on Tuesday after oil spilled into the water at Walsworth Common.
Several more ducks were rescued by RSPCA staff on Wednesday and yesterday.
One inspector waded into the water and drove the animals towards colleagues who waited on the bank with nets.
Each bird was cleaned and then taken to Tiggywinkles Wildlife Hospital in Aylesbury, Buckinghamshire, where they were fed carbon to counter the damaging effects swallowed oil.
The cause of the oil spill was sill unknown yesterday.
RSPCA inspector Peter Green, who was among the group that rescued the birds, said: "It was quite a serious mess really. It's pretty unusual for it to be so bad. It is not at all good for the birds to be covered in oil. It stops them flying and means they are not waterproof so struggle to float on water."