Stephen Frost killed a kea while at work in the Motueka Valley because it was noisy and had annoyed him.

A Nelson man who killed a kea after throwing a piece of wood at it told his co-workers, "it's just a f...... bird".

Stephen Frost, 46, faced two charges under the Wildlife Act of hunting or killing protected wildlife and disposing of protected wildlife without lawful authority. He pleaded guilty to the charges in the Nelson District Court on Wednesday.

The maximum penalty is a fine of up to $100,000 or a two year term of imprisonment. It is an offence to hunt, kill, or possess any protected wildlife in New Zealand.

Last July, Frost was working at a construction site at Stanley Hill in the Motueka Valley where kea were frequently seen. There had been reports of kea causing some damage to equipment.

Frost's employer had advised staff that kea were protected and given practical solutions to working in an environment where the birds were present.

Despite this, Frost had been seen displaying hostility towards kea, shouting at the birds and throwing objects at them on a number of occasions.

BARRY HARCOURT/STUFF Kea, the world's only alpine parrot, are nationally threatened. It is believed there are less than 5000 remaining in the wild.

On the morning of July 18, Frost and some of his co-workers were in an office on the site when they heard kea on the roof.

Frost went outside and saw kea on a shipping container making noise. He picked up a 30cm solid wood builder's peg and threw it at the kea, hitting it and knocking it off the container.

He then stood on the injured kea's head.

A co-worker arrived to find Frost standing over the kea, which was still moving. It then stopped moving and died from its injuries.

When confronted by his co-workers, Frost reportedly said, "it's just a f***ing bird".

He then wrapped the kea in black plastic and put it in a skip bin on site.

A Department of Conservation ranger visited the site the following week and located the dead kea in a bin. He spoke to Frost who admitted to killing the bird. He said he didn't mean to throw the peg, he wanted to scare the kea away, but it was icy and the peg slipped out of his hand.

He claimed he panicked after hitting the kea and said it was "pretty stuffed" so he decided to put it out of its misery by "stomping on its head".

Frost said the kea made a lot of noise and this had annoyed him as he was stressed out about his father's ill health.

"I knew they were extinct and everything."

Kea, the world's only alpine parrot has been protected in New Zealand since December 1986. It is estimated fewer than 5000 kea remain in the wild and their conservation status is threatened.

Kea Conservation Trust conflict transformation co-ordinator Andrea Goodman said it was "intolerable" that someone would decide to kill kea.

She said the trust had visited the Motueka building site to look at ways it could be less attractive to kea and had been working with the project manager prior to the incident.

ALDEN WILLIAMS/STUFF Frost told a DOC worker that the kea was "pretty stuffed" so he decided to put it out of its misery by "stomping on its head". (File photo)

Actions included making sure there was no food left lying around, shutting doors to vehicles and the smoko room and keeping the site tidy so there was nothing lying around for the birds to get into. She said the landowner and his team had done everything right.

She said the worst thing someone could do was feed a kea, because once a bird was fed it would continue to seek food from people.

Goodman said kea were naturally inquisitive and when they left the nest, they would mob up and fly around together.

"For young kea, which these kea were, putting things in their mouth and playing with them is how they learn about the environment around them."

Goodman said while they were alpine birds, kea were often found at lower altitudes so it was important people learnt to live with the parrots.

"Kea have a hard enough life as it is being ground nesters, they are vulnerable to predation and we have got to make sure they are well looked after.

Frost will be sentenced in the Nelson District Court on January 23.