About 40 black-backed gulls have died. Photo: floraandfauna.co.nz
The news comes after it was confirmed that more than 1000 waterfowl died near the Waikouaiti wastewater treatment plant in Otago, after being infected with the disease.
Senior biodiversity ranger Ian Fraser said botulism looked to be the cause at Washdyke, and tests would rule out any exotic disease.
Avian botulism is a naturally occurring bird disease triggered by environmental conditions which prompt a bacteria, found naturally in soil, to produce a toxin that causes birds to die.
Outbreaks are localised and clear naturally when conditions change.
Doc said it was monitoring the situation and planned to collect and dispose of some of the carcasses to reduce the spread to other birds.
