It may be an impossible mission, but Auckland Zoo staff are hoping they can help bring the Fatu Hiva monarch back from the brink of extinction.

The Fatu Hiva monarch is endemic to the island in French Polynesia, about 1100km north of Tahiti and accessible only by boat.

The small flycatcher with purplish-black feathers was once common throughout Fatu Hiva Island, but are now critically endangered due to introduced predators such as tree-climbing rats and cats and the fairly recent emergence of avian malaria, a disease spread by mosquitos.

There are now only about 19 left Fatu Hiva monarchs left, with only five females in their prime for breeding, making the species one of the world’s rarest.

“This bird has a role in its ecosystem. If this bird disappears, the functions of that bird will disappear in the ecosystem, and that may have unknown consequences for the rest of the ecosystem,” said Richard Gibson, Auckland Zoo’s head of animal care and conservation.

The zoo and the Société d’Ornithologie de Polynésie/Manu SOP (Polynesian Ornithological Society) launched an emergency breeding program to help save the bird from extinction in July.

The program sees Manu SOP biologists monitor eggs in their nests before collecting them near the end of their incubation period, Gibson said.

What is unusual with Fatu Hiva monarchs, he added, is that they only lay one egg at a time.

When the eggs are close to hatching, Auckland Zoo bird specialists scramble to the tiny island nation, which is only accessible by boat, to hatch – and hopefully rear – the chicks in a purpose-built facility.

Successfully reared chicks will be released into a predator and mosquito-proof aviary.

At Auckland Zoo, hand reared birds are fed minced baby mice, which the zoo buys frozen. But “the last thing we need to do is take mice on an island that’s already got a rat problem”, Gibson said.

Instead, the chicks are fed non-native geckos and lizards introduced to the island, which are a part of the birds’ natural diet.

“If you’ve committed to working with animals and wildlife and conservation, then the killing of any animal is not done lightly,” said Auckland Zoo director Kevin Buley.

“The potential benefits of being able to save these species by killing the introduced gecko in a humane way… The potential ends justify the means.”

Since the programme began in July, about three eggs have hatched. However, the chicks died just a few days later.

Thyroid issues detected in the chicks could be the result of inbreeding.

“None of it’s gone smoothly,” Gibson said.

It’s unlikely the chicks died due to human intervention, as the birds are taken from the nests late in their incubation period when they are nearly fully developed.

“We’d be very surprised if it’s anything that we’re doing wrong… Their incubation parameters are excellent and would work for any other species we’ve ever worked with.”

“It’s much more likely that we’ve got an inbred population of birds, some of which are elderly breeding birds now, producing low quality, possibly disadvantaged embryos/eggs.”

Each time an egg is laid, a difficult decision must be made, Gibson said. If every egg so far has failed to produce a live chick, should the next egg be left alone?

“We can leave it in the wild, and it may or may not fledge in the wild, but ultimately it won’t help save the species in the wild.

“The species is not going to survive without an increase in numbers, and the only way to increase the numbers is through intensive management.”

But it could be too late.

“If I’m brutally honest, I think we might be on a hiding to nothing,” Gibson said.

So, why put in so much effort into a bird that may be beyond help?

“Everything’s worth saving, I don’t need a why.”

“I care about the smallest to the largest, the most beautiful to the ugliest, they all deserve to be here.”

“It’s definitely doable, but the odds are stacked against us. We have to exploit every opportunity to try new things.”