Wildlife experts were called after an oil spillage contaminated a waterway.
Neighbours said oil had been dumped in a dyke behind their homes in Scrapsgate, Minster, on the Isle of Sheppey.
One wrote: "All the ducks and at least two ducklings, a heron and probably the egrets are plastered in black muck. I have informed the Environment Agency and they should send someone to take a look as that water filters into the sea."
The message was sent to Ray Allibone of Swampys Wildlife Rescue on Tuesday.
He said: "We may not know the full impact of this for a couple of days. I am also concerned about water voles and other wildlife living on the banks of the stream."
He said he had put a swan sanctuary on standby in case any of Sheppey's swans were affected.
One neighbour, who did not want to be identified, said: "I've lived here for 22 years and never seen anything like this before. It looked like oil had been dumped in the middle of the stream.
"We only noticed it when the ducks came to us to be fed in the morning. My daughter said it looked as if they were covered in oil. They were all black."
Minster parish councillor Dolley White was also at the scene and pledged any help she could offer in the clean-up operation.
But by the time Mr Allibone arrived most of the oil appeared to have dissipated with just a thin film left on the water surface. He was also unable to find any birds affected by the spillage.
He said: "There were a couple of ducks preening their feathers but they were able to fly. They could not have done that if they were covered in oil."
He had previously warned that if any animals had swallowed the oil they might have to be put to sleep.
The oil is believed to have been dumped in the stream at the end of Marian Avenue. It runs parallel with Scrapsgate and through the Abbey Hotel and Lazells nightclub sites before ending at the White House restaurant.
An Environment Agency spokesman said: “We are aware of the reported pollution of the dyke. Although a small film has been seen on the surface on the water we believe it poses a low environmental risk.
"We haven’t received any reports as yet of wildlife being adversely impacted. We are thankful to members of the public for reporting pollution on our hotline number 0800 807060.”