In recent weeks, the group’s volunteers have responded to several calls to treat birds which all presented signs of poisoning and eventually died. 

Group spokesperson Belinda Gales said poisoning was the likely cause.

“There have just been too many for it to be a coincidence,” she said.

The birds are mostly raptors, owls and tawny frogmouths.

“We believe the cause is the cumulative effects of insecticides in the prey and insects they feed on,” she said.

“The tawny frogmouth, for example, feeds exclusively on insects and can eat hundreds in a night.

“We have had up to six birds die by what is believed to be secondary poisoning. 

“Even a brushtail possum was reported to have been affected by the poison.”

The insects include common ones, such as grasshoppers, found in gardens.

Ms Gale said the deaths could also be the result of secondary poisoning when raptors scavenge on dead animals that have eaten insecticide or rodent poison.

“Birds, however, appear to be more sensitive than other vertebrates to the toxic effects of the pesticides,” Ms Gales said.

Birds can be exposed to pesticides by eating treated seeds or vegetation, poisoned insects, carrion killed by pesticide, baits and drinking contaminated water.

Poisoned birds exhibit signs such as convulsions, lethargy, paralysis and tremors.

The group urged people who applied pesticides to consider wildlife and take note of the environmental and seasonal conditions when they use the chemicals.

It said the malicious use of pesticides was illegal.