"It would not be acceptable for a colony of dogs, stoats or rats to remain in the same way this cat colony is," Mr Windust said. "We are offering $600 toward the costs associated with [euthanising] the cat colony in an effort to save our native wildlife in the area. We do not want to see these cats re-released anywhere else."
Bay of Islands SPCA boss John Logie said his organisation had no involvement with the cat colony, but it was one of several in New Zealand run by volunteers to ensure the cats remained well-fed and healthy rather than becoming an urban problem.
The Paihia colony was well run by Betty Chapman, and organised by a completely separate volunteer group from the SPCA - "who may, like anyone on the planet, belong to the SPCA as a member", Mr Logie said.
The group of locals met the cats' daily feeding, desexing and vet costs with their own money, receiving no funding from the Bay of Islands SPCA, he said.
Mr Windust said Bay Bush Action volunteers often trapped cats among the targeted predators - possum, rats and stoats - in the Opua State Forest, local bush and the small islands off Paihia.
Feral cats were hard to catch and many were killing birds, geckos and other native creatures in the area, he said. He had found a whole, freshly eaten forest gecko in the stomach of a feral cat he had caught in a trap recently.
"We have endangered New Zealand dotterel feeding and flocking on our beaches with a stray cat colony established only a few hundred metres away. It's ridiculous," Mr Windust said.
"Paihia is lucky to be one of the most biodiverse residential areas in New Zealand. As a community we need to have pride in our wonderful native wildlife and start standing up for them.
"Cats will never go extinct, but our native flora and fauna is hurtling towards it unless we start to turn the tide. Removing the homeless cat colony is one step in that journey."
Bay Bush Action has a partnership agreement with the Department of Conservation to carry out pest control in the Opua Forest backing on to Paihia and Waitangi. Its volunteers also carry out beach clean-ups.