Reported by BBC Science
A major recovery effort is continuing after an oil spill caused by the vandalism of a nearby home heating oil tank resulted in the death of 13 birds from Broughshane Waterfowl Park.
More than 20 birds were transported to the USPCA's headquarters last week for urgent specialist care, but the death toll has continued to rise.
The popular attraction in County Antrim has been forced to close while efforts continue to remove oil from the pond.
More from the original report
Police have appealed for anyone with information to come forward.
More than 20 animals were treated by a vet and transported to the USCPA in Newry
Broughshane Environment Wildfowl and Wildlife Trust's chairman, Gary Hayward, said they incident had been a "nightmare".
"One of our volunteers appeared on the Thursday morning to feed [the birds], and walked down through the park and smelt this kerosene smell and saw the black swans completely oiled."
The park is home to 120 "collection birds", as well as wild birds, he explained.
"So far we have lost 13 birds, some of which are really close to us."
Hayward praised the efforts of the USPCA and Northern Ireland Environment Agency (NIEA), who have been instrumental in treating the sick birds and clearing up the spillage.
The pond has become well known for its variety of waterfowl and has been in existence for 13 years
The Northern Ireland Environment Agency (NIEA) was first alerted to the incident on Thursday 22 October and have been involved in trying to remove the oil waste.
"The incident was quickly confirmed as having had a significant impact on the ponds and NIEA inspectors deployed oil absorbent booms and other countermeasures as mitigation," a spokesperson said.
The agency said the substance involved had been identified as home heating oil, or kerosene, and that the source had been traced to a nearby tank.
The waterway is noted to be much improved but further works will be carried out as long as is deemed necessary.
Gary Hayward believes it will be weeks before the park can return to normal
Hayward hopes that the incident will be an…