A depiction of what a live South Island kōkako would look like, using a photoshopped image of a North Island kōkako (which has blue rather than orange wattles)

A possible sighting of the South Island kōkako in Golden Bay has raised hopes that the "grey ghost" lives.

When Liam Beattie walked the Heaphy Track last month, he was hoping to catch a glimpse of one of New Zealand's rarest birds.

Instead, he may have stumbled across another which was supposed to be extinct.

Having heard about the release of endangered takahē into Kahurangi National Park, Beattie and his father decided to have a look for the rare bird during their tramp on the Heaphy between the West Coast and Golden Bay.

However, the bird Beattie saw while wandering near the Gouland Downs hut was not a takahē.

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It was larger than the other birds in the area, with grey feathers and two distinctive orange wattles on its neck.

Beattie said it flew onto a low-hanging tree branch, hopped to the ground and then flew away after about 10 seconds.

ALDEN WILLIAMS & CHARLES ANDERSON/Stuff.co.nz Nelson Mail reporter Charles Anderson on the hunt for the South Island Kokako

"It was just chilling out, it seemed pretty relaxed and didn't seem to be in a hurry to go anywhere."

Beattie noted the bird seemed unusual, but didn't think much more of it until arriving at the DOC hut after an hour or so.

On the wall of the hut was a picture of a bird with the caption "Wanted: preferably alive - South Island kōkako $10,000 reward".

"Initially I thought it was a joke – that was the bird I had just seen."

Once he realised significance of the sighting, Beattie got in touch with the group responsible for the poster, the South Island Kōkako Charitable Trust.

Since January 2017, the kōkako, known as the "grey ghost" has been the most wanted bird in the country, with the trust putting up a $10,000 reward to anyone who can provide photographic evidence of it in the wild.

The last verified sighting of the South Island kōkako in the 20th century was in 1967, with the species being officially declared extinct by DOC in 2008.

Gerard Hindmarsh The Gouland Downs on the Heaphy Track was the site of one of the most promising kōkako sightings in recent times.

However, after a 2007 sighting near Reefton was accepted as accurate, DOC upgraded the bird's status to 'data deficient' in 2013.

Ornithologist and long-time kōkako searcher Rhys Buckingham said Beattie's sighting was one of the most encouraging in recent years.

"I think it is a highly rated one. The observer saw it at close range, and it had the right colour and the right movements."

In October more potential kokako discoveries were made, this time on the Takaka Hill between Riwaka and Golden Bay.

One person recorded an audio file of a birdsong resembling a kōkako, with another catching a glimpse of large grey bird while driving over the hill.

Steve Catalinac said he saw two birds, one of which flew across his path while travelling down towards Takaka.

"It lasted about two or three seconds, after I saw it I didn't believe it myself for a moment.

"It was a grey colour, bigger than a tui and definitely not a woodpigeon – I'm pretty certain it was a kōkako."

South Island Kōkako Charitable Trust The South Island Kōkako Charitable Trust has been compiling a map of recorded sightings of the bird, which was declared extinct until 2013, when its status was upgraded by DOC to 'data deficient'.

Buckingham said while an area like the Takaka Hill would be difficult to search with it's rugged terrain, there was no reason why there couldn't be a bird in the area.

South Island Kokako Charitable Trust general manager Inger Perkins said the recent sightings had brought the total number of reports since the campaign started to 120.

In their own research, Perkins said the trust had found about 430 reports or sightings of the bird since 1990.

"The reports are coming from all over the place," Perkins said.

"When we started the public launch for the search in January last year, we were hoping it would help us narrow down the areas, but its actually broadened it out."

Geoff Reid Kokako enthusiast Rhys Buckingham on the lookout for the bird on the West Coast, near Haast.

While many people have claimed to hear or see the bird since the campaign started, photographic evidence remains elusive.

Buckingham said unlike their North Island relatives, the South Island kōkako had always been difficult to pin down.

"They're still around, they're still breeding, but it is in such low numbers.

"If you've got a really quiet bird out there in the forest, it's going to be really hard to detect."

With the probability of so few birds being left, Buckingham said it was likely the bird was "functionally extinct".

He said there was still hope for the kōkako if live birds could be captured, either matching breeding pairs or cross-breeding them with the North Island species.

"That could start the process of saving the bird. We've already lost so many, but this one is so special.

"The call of the kōkako is stunning – they've just got to call more."