Experts are still investigating what led to the sudden deaths of dozens of ducks and coots at Sandall Park - but there have been suggestions that the birds may have eaten remains from bins, including the leftovers of chicken from a nearby KFC branch and mouldy bread.
It is understood that the deaths are being treated as a case of animal botulism - and could have been caused by ducks eating rotting food which has become infected during the recent heatwave.
One local wildlife enthusiast, David Johnson, said: "My theory is that the ducks could have eaten chicken remains from the bins, which of course, in this hot weather, would have been particularly unpleasant after a few days.
"I know lots of people use the KFC over the road and then eat their food in the park, leaving the remains where the ducks can get at them."
There have also been reports of people spotted feeding the ducks chicken.
Doncaster Council has ruled out bird flu as the cause of the deaths.
Dave Wilkinson, the authority's assistant director for Trading and Property Services, said: “We are continuing to liaise with the Animal and Plant Health Agency to establish the cause of death of the ducks at Sandall Park.
"We have confirmed that this is not a case of bird flu.
"We would like to reassure the public that there is no risk to them and this is only affecting birds.
“As a precaution, we would encourage the public visiting Sandall Park to keep dogs on a lead, not to swim in the lake or touch the ducks.
"If you do accidently come into contact with the ducks then immediately wash your hands. The situation will continue to be monitored and assessed."
The park's lake has been sealed off and signs erected warning visitors to stay away from the water and ducks - although the park is still open for business.
Sandra Crabtree of Friends of Sandall Park, the volunteer group which looks after the park, said: "The issue could well be mouldy bread. Feeding bread to the ducks might seem like an old tradition, but bread is not good for them and any bread which is left in the water can become mouldy.
"There are plenty of things people can feed the ducks but bread isn't one of them."