A duck rescue group is worried that a deadly disease, which is killing off hundreds of birds in Auckland parks, could also spread to other animals.
The birds have been struck down by avian botulism, which is produced when natural bacteria heats up in the water.
The disease is made worse by the actions of the public - sharing leftover bread with ducks is causing harm to the animals.
Park local Chris Yoxall said humans tend to make it worse, particularly in the ponds.
"Lots of people feed the ducks and they're fed very poor food," he said.
"White bread in particular just isn't good for ducks."
Even if the bread is not eaten right away, it still harbours the disease, meaning ducks that eat it days later can become critically ill or die.