The 11 surviving ducks, all mallards, were being treated Thursday at the Wetlands & Wildlife Care Center, where volunteers provided the birds with antibiotics, fluids and an anti-serum for botulism.
“My gut feeling is, it is botulism,” said Debbie McGuire, wildlife director at the center. “A lot of times, people are throwing bread into lakes, and cause nutrient botulism to get going.”
The surviving ducks appeared to be doing well; the most recent ailing duck arrived from the regional park Thursday.
“They’re walking, starting to self-feed, starting to gain strength,” said Terri Oba, a wildlife technician at the center.
The first to get well could be released next week, she said.
Birds with botulism poisoning typically cannot stand or hold up their heads; some arrive at the care center gasping for breath, Oba said.
Laguna Niguel park is home to a lake popular for fishing. But any decaying animal or vegetable material — or food, such as bread — can give rise to the bacteria that produce the botulism toxin with the right combination of conditions: heat, a watery, low-oxygen environment such as the margin of a lake, and little or no circulation of water.
Birds might acquire the toxin by eating the rotting material, or maggots — fly larvae — that feed on the decaying matter, or just from the water itself.
Warnings posted at county parks with lakes urge visitors not to feed the birds, to help prevent such outbreaks, said spokeswoman Marisa O’Neil.
The first duck deaths were reported Sunday.
It was unknown Thursday whether any of the duck carcasses would be sent out for laboratory testing to confirm botulism poisoning.