RSPCA inspectors have called for the clear-out of a Northampton lake after deep mud saw them struggle to save dying birds caught up in an oil spillage.
The lake, off Crestwood Road, Thorplands, was polluted with a film of oil over the weekend and, although the RSPCA and volunteers saved several water fowl, four cygnets have died.
Michelle McNab, of the RSPCA, said they tried to reach at least 15 more birds but have been defeated by the knee-deep mud, caused by a grate to the channel that feeds the lake being stuffed up with litter.
The Chron last reported the issue in 2012 but nothing has been done by Northampton Borough Council since.
Mrs McNab said: “We don’t yet know where the oil has come from, but we do know that the state of the lake needs to be a whole lot better than this.
“There are coots standing out there that we could have used a boat to reach. You take a step into the mud and you literally get stuck up to your knees.
“One of our volunteers had to be dug out on Monday morning.”
So far, seven ducks, a swan and some cygnets have been rescued, but four of the cygnets later died of the effects of oil ingestion.
The oil rids feathers of air, so makes birds cold and prevents them from diving.
But they also get poisoned by the chemicals, with some of the ducks seen with fuild pouring from their nostrils and mouths.
The rescued birds will be taken to a sanctuary so specialists can attempt to clean them using washing-up liquid.
The Environment Agency said it had installed a boom to try to absorb the oil and was consulting with Anglian Water about the source of the leak.
A Northampton Borough Council spokeswoman said: “We sent park rangers to the lake this morning and informed the Environment Agency as soon as we became aware of the incident. The rangers also helped the RSPB to rescue the birds. The dredging of the lake is currently being looked into as a capital project.”