An investigation is underway after a spate of dead ducks and corellas were found near a lake in inner-city Sydney.
Local wildlife rescuers, the City of Sydney, and the Australian Registry of Wildlife Health at Taronga Zoo are looking into the cause of about 25 animal deaths at Victoria Park in Camperdown.
Kelly Murphy from Sydney Wildlife Rescue said they had responded to calls about animals dying over the past two weeks. She says they have never seen an event with this many animal deaths at this location.
"We get there when they're alive but they're very, very close to death," Ms Murphy told ABC Radio Sydney.
"We are transporting them to local vets to try and treat them but unfortunately we don't have any survivors at this stage."
She said they were first notified of a potential problem two weeks ago when seven dead native ducks were found.
A council spokesperson said urgent water testing of Lake Northam did not identify a likely cause of the deaths.
"Additional testing to find a possible soil-borne bacteria is being carried out with results due back shortly," the spokesperson said.
"Unfortunately, duck deaths are not uncommon during warmer months. Expert advice indicates the risk to other aquatic wildlife and the community is low."
Ms Murphy, a waterbird specialist, said more recently birds and a flying fox were being found with evidence of paralysis.
National Parks and Wildlife Service says it is aware of the bird deaths and will monitor the results of tests to determine if a response is required.
Botulism suspected
Ms Murphy suspects the cause may be botulism from low oxygen in the lake's water following the recent extreme heat and a covering of weed.
"The duckweed that the ducks love grows a lot on top of the lake and actually stops more oxygen getting in," Ms Murphy said.
"So it's a combination of hot weather, low water flow, low oxygenation in the water. This is what we believe.
"The Lake Northam wetlands in Victoria Park, it's a particularly shallow lake."
Ms Murphy said the cause was not anything for people to be alarmed about as the illness was only likely to spread between bird populations.
"It can particularly spread amongst waterbird populations," she said.
Sydney Wildlife Rescue is urging local residents to watch out for sick or injured birds that may have travelled from the park to contact them or WIRES.
ABC Radio Sydney has contacted Taronga Zoo for comment.
