A stuffed South Island kokako, or "grey ghost" thought to be extinct, but the subject of many unconfirmed sightings in recent years.

Six hundred years ago a Haast's eagle with its 3-metre wingspan swooped on a 3.6m tall moa, grabbing the giant bird with its tiger-sized claws before crushing its skull in a vice like grip.

Of course, both species are long gone so its extinction is hard for us to relate to. However, many of our natural treasures have been lost in our own, our parents' or grandparents' lifetimes. They share many similarities to species we know and love today, which raises the question: if we can lose them, what's to stop us losing others?

Twice the size of the morkpork/ruru, the laughing owl/whēkau was named for its call, which was "a series of dismal shrieks" – perhaps a little tongue in cheek. The last confirmed sighting was in 1914, although some people claimed to have seen them since. They co-existed with people until stoats, ferrets, weasels and other predators increased in numbers.

The greater short-tailed bat was last seen in 1965, and its extinction was likely caused by a rat invasion on its last island home, Big South Cape Island in 1963. Related to our existing lesser short-tailed bat, it is assumed that it too scuttled around on the ground, using its wings like legs, feeding on insects, fruit, pollen and nectar.

READ MORE:

* On a Grey Ghost hunt

* Fossil of 'extinct' bat found in Otago

* South Island kokako sighting near Nelson

The bush wren/ mātuhituhi disappeared in 1972. Six birds were translocated to a nearby island after the same rat invasion on Big South Cape Island, but did not survive. The bush wren belongs to the same genus as the rock wren/pīwauwau which is under threat from stoats in its home along the Southern Alps.

And then there is the infamous South Island kokako – the debate continues about whether it's extinct or not, and many continue to 'see' the "grey ghost", elusive in the forest shadows.

It was reclassified as data deficient in 2013 after being declared extinct in 2017. It's a race against time but a dedicated bunch of enthusiasts are determined to prove its existence with the hope it can be brought back from the brink.

The possibility of bringing a species back from the dead is not new - takahē were thought to be extinct until small numbers were rediscovered in the Murchison Mountains of Fiordland in 1948. The species reached a milestone recently by moving from "Nationally Critical" to "Nationally Vulnerable". There are now 347 of them!

In the 750 years since human arrival, we have lost 76 species of birds, three frogs, three lizards, one fish and an unknown number of invertebrates. The grey duck is likely to be next on the list – it has hybridised with mallards to such an extent that there aren't many purebreds left. There are only around 40 fairy terns and 300 orange-fronted parakeet/kākāriki karaka left.

The tide can be turned with intensive management: kākāpō reached their lowest population size of 50 in the 1990s but have since tripled to 154. Black stilt/kakī have increased from 23 in 1981 to 106 with captive breeding programme. The black robin/kakaruia population may be our most significant programme of all, with only one breeding female left; her descendants now exceed 250.

It's easy to feel overwhelmed and helpless with such statistics but there is strength in people working together. You can help by joining volunteer groups, starting your own community project or even running a trap in your backyard. With more people working towards the goal of a Predator Free New Zealand, let's hope we don't lose any more of our natural treasures.

For more information about predator free and trapping go to www.doc.govt.nz - predator-free-2050.