Broughshane Environment Wildfowl and Wildlife Trust’s chairman, Gary Hayward, said they incident had been a “nightmare”.
“We are devastated,” he told BBC News NI.
“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.
