Up to 800 birds have been found dead at wetlands in Christchurch's eastern suburbs and the oxidation ponds.

The Christchurch City Council said yesterday that during the past few weeks dead birds have been found on the banks of the oxidation ponds in Bromley.

Dead birds have also been found in the Bexley area and the Travis Wetland.

Council ornithologist Andrew Crossland said between 600 and 800 dead birds had been found.

"The earthquakes in Christchurch have caused a lot of changes to water quality but also to effluent levels at the oxidation ponds," he said.

"It's got nothing to do with anything physical such as liquefaction but more to do with the fluctuating water levels and changes like that."

Investigations were underway but the initial diagnosis was avian botulism, a paralysing disease caused by a toxin which thrives in shallow, warm water.

Avian botulism can not be transferred to people.

However, the council was urging people and animals to avoid infected or dead birds until specialist testing was complete.