New Zealand conservationists are worried at the rapid decline in the number of kea, the world's only alpine parrot.

Kea Conservation Trust volunteer Mark Brabyn told Nine to Noon that predators such as stoats and possums were linked to their rapid decline.

He estimated the kea population, which was concentrated in areas around Arthur's Pass, and the Fox and Franz Josef glaciers, at about 3000 to 4000.

"There may be a few more, but it's the rate of decline that's what's alarming us the most," Mr Brabyn said.

He said kea were increasingly attracted to places where tourists gathered, including South Island ski fields.

And human interaction was a problem, especially when people fed them, he said.

"Keas are one of the major dispersal animals for a lot of our alpine plants, so by keas eating muffins and pies and things, they're not eating the actual berries and dispersing all our native plants," he said.

Mr Brabyn said it was also a problem when kea started "hanging around" towns, where they ate things they should not, such as lead nails.

He said a kea was recently treated for lead poisoning, linked to its diet.

Predators like stoats, possums and cats were also taking their toll on the species.

A number of kea nests and a group of critical breeding females had all been destroyed in recent years, he said.

The kea population was most at risk during seed production (mast) years, which triggered an increase in mice.

"And then the stoats increase because there all these mice to feed on, and then when they die in winter the stoats then switch to birds, including kea," Mr Brabyn said.

He did a lot of back-country tramping, and in the last 20 years had noticed a real decline in kea.

"You go to areas where there's no predator control and you're lucky to see one or two. Friends have been in Fiordland where there've been none sighted."

The trust has started a citizen science project to encourage the public to help monitor the birds, and to help support a tagging project. And a Givealittle page set up to raise funds attracted $6000 in its first week, and currently sits at over $8000.

The trust has set a target of $30,000.

Mr Brabyn said they planned to set up a kea display in Arthur's Pass, a website and a brochure that included a form for people to record kea sightings. It would also be developed for online users, via mobile phones.

"We want to involve the public, tourists, backpackers, trampers. We want them to record the kea and get to know them," Mr Brabyn said.