Ducks at a picturesque Mottingham park have been "decimated" by pollution at their lake - the second tragedy there in five years.
Visitors to the Tarn have been distressed to see swans and ducks struggling in thick green algae brought on by the combination of silt from rain water and periods of hot weather.
A duck being rescued in 2009
Carole Thomas from the Friends of the Tarn group said the resulting botulism meant around 60 ducks and geese had gone from the lake, along with 12 goslings, seven tufty ducklings and another 15 ducklings.
Michael Molloy, 78, from Sidcup, was at the Tarn with grandson Harry, 11, when he saw the "absolutely dreadful" scenes. He said: "There was a Canadian goose stuck in the middle of the thick green algae and it couldn't move.
"We were throwing bread to it but it just didn't have the energy. It was ghastly."
The birds have also struggles with discharged water from nearby homes, blamed on misconnected appliances like washing machines or waste thrown down drains.
Filthy discharge being washed into the lake
Ms Thomas said: "The Friends on a weekly basis scoop out elsatic bands, cigarette ends, polysterene cups, condoms, drinks cans. In fact, you name it, we have found it in the Tarn washed down by the rain.
"A tremendous amount of silt is also washed down off the roads which includes carbon emissions from diesel engines. This then means that the Tarn holds less water and therefore the toxins are much more concentrated."
Back in 2009, a similar incident poisoned 50 birds, although, with help from husband and wife team Willow Wildlife Rescue and their animal ambulance equipped with mini stretchers and drips, some were saved.
The Friends - who have been talking with Greenwich Council, Thames Water and the Environment Agnecy - say they need people to be more aware where their rubbish ends up, for misconnections to be tackled and for de-silting to happen.
And Ms Thomas said: "This is the second major outbreak we have had, the last being five years ago. If a solution is not found then this will not be the last."
Ward councillor Coun Spencer Drury said: "I found out about the ducks when I popped into the Tarn for some tea and cake and was confronted with the scene of an RSPCA officer retrieving a dead duck from the lake."
He added: "The whole situation has come about because the council has failed to produce a decent plan - not ensured that houses discharge pipes go into the sewer rather than the Tarn, failed to clear the lake and allowed botulism to recur when reasonable precautions could have been taken.”
Ducks in the animal ambulance in 2009
A spokesman for Greenwich Council said: "We share the concerns raised about the plight of a number of birds at the Tarn’s lake and have been working with Thames Water, Environment Agency and others on measures to tackle the situation.
"The problems are the result of botulism, which occurs naturally in silt and lays dormant until conditions allow it to multiply and become toxic to birds. The RSPB has confirmed that they are receiving lots of reports of avian botulism at the moment, brought on by the recent very warm weather.
“Because of the natural way the disease is formed it is difficult to completely eradicate avian botulism, but we have introduced measures to help to contain it where possible.
"Following a similar outbreak in 2009 reed beds were planted and a pump fitted to help improve oxygen levels. The pump continues to be used and we have increased the hours it is operated. The original reed beds were grazed by the birds, so additional reeds have been introduced more recently.
"The lake is inspected daily and any ill or dead birds are removed by officers, with the help of members of the Friends group to help control the spread of the disease.
“Thames Water have been installing and maintaining additional booms which collect floating pollutants which come through the culvert and are continuing to trace any illegal connections to the water course following a recent pollution event upstream. The Royal Borough is also receiving quotes from contractors for further de-silting works in the Autumn.
“There is no risk to public health as this strain of botulism only affects birds. However, we recognise that visitors will be very concerned about the effects on the local bird population, and we continue to work with partners to tackle the problem.”