A New Zealand charity is offering 5,000 NZ dollars ($A4,800) for sightings of a South Island kokako - but there's a catch: The endemic bird species is most likely extinct.
The bird, with a distinctive orange wattle under its neck, is unique to New Zealand and was once widespread in the forests of the South Island and Stewart Island.
Before 2013 it was listed as extinct, but after some credible sightings it was reclassified as "data deficient," thus triggering the search for more information.
The hunt for what could well be the rarest bird on the planet is urgent, the chairman of the South Island Kokako Charitable Trust, Euan Kennedy, said on Thursday in a statement.
"If South Island kokako still exist, there will be very few left. We need to locate them very soon so that conservation has a higher prospect of success," he added.
The reward would be paid once a panel of New Zealand's expert ornithologists agreed that the bird exists.
Trampers, bird-lovers, hunters and all other backcountry users who think they've seen or heard the bird can register the sighting on the trust's website.
As no photo of the bird exists, the trust has released a digitally altered image of the North Island kokako to give people an idea of what the South Island variety would probably look like.
In the early 1800s, the kokako occupied large parts of the South Island but numbers declined quickly after the introductions of cats, ship rats and stoats, and the birds were very rare by the late 1800s. The last confirmed sighting was in Mount Aspiring National Park in 1967.
