Critically endangered yellow-crested cockatoos found an unexpected sanctuary among Hong Kong’s towering skyscrapers, but like their human neighbors they now face trouble finding a place to call home.

Native to Indonesia and East Timor, the snow-white birds, their crests flashing like yellow crowns, squawk through the urban parks of the Asian financial hub.

They make up roughly 10% of the species' global wild population, which numbers only up to 2,000 mature birds.

Research shows the city’s cockatoo population has stagnated as the birds, which live in tree cavities, are losing natural nesting spaces in old trees due to typhoons and government tree trimming for public safety.

That's adding to global pressures on cockatoos such as the illegal pet trade and climate change.

Hong Kong's conservationists have stepped in with a solution: installing artificial nest boxes that mimic these natural hollows.

Dr Astrid Andersson has been studying the Hong Kong Cockatoo population for nearly a decade.

Andersson believes the now wild population started off from birds who were imported as pets.

She says: “Cockatoos in general are a very popular pet. And in the 80s and 90s, because of the huge export from Indonesia, yellow crested cockatoos were very available. And so a lot of people had them as pets. But what I think happened was they didn't realize that these birds are very long, long lived. They will live for up to 80 years in some cases. And they're also very noisy. They're very messy. So what happened was I think either pets were escaping because they're also very clever, or they were being released. And that's how this wild population came to grow and become established in Hong Kong's city centre.”

Because the number of juvenile birds is unusually low Andersson and conservationist Henry Wong are trying to recreate the

habitat which will encourage the adult birds to nest.

Henry Wong is fitting a replacement nest they hope will be the solution.

The nest boxes are hollow and cylindrical aiming to mimic the trees they are being strapped to.

Researchers also hope cameras in the colony of nests will allow them to track cockatoo behaviour and closely study how they reproduce so the scientists can help support future generations.

Wong who helped develop the nests says similar strategies have been used in Australia, although those nests weren't suitable for the Hong Kong birds and had to be adapted.

He says: “Actually, there was an initial reference design, which was a nest box used in Australia. Dr Astrid mentioned that this type of nest box was successful there. But once it came to Hong Kong, there are differences in both the climate and the specific needs for university research purpose. For example, a camera needed to be installed inside, and the ventilation had to be improved. So, starting from that design, we made modifications and added different functions to the nest box, and eventually it turned into what you see now.”

Early signs are promising, with at least one pair of cockatoos already exploring them.

Andersson says: “I have to say that we have this amazing, unique opportunity here because we have almost 10% of the remaining wild population for this species on the planet. So in Hong Kong, we have between 150 and 200, somewhere in between there and globally in Indonesia and East Timor, which is where they come from originally, there's around a 1,500 to 2000 according to the IUCN (International Union for Conservation of Nature).”

Andersson believes it may even be possible for the Hong Kong population of Yellow-crested Cockatoos to restore dwindling populations in Indonesia and East Timor.

But she warns that without monitoring and adequate breeding opportunities, the city’s birds could decline in coming decades, and rare chance to contribute to global conservation will have been lost.

“There really are ways for us to create small things in this city that allow the animals living here to coexist with us in this shared space. So it has been a really valuable experience,” says Wong.

Once widespread across island chains from central to eastern Indonesia and East Timor, the yellow-crested cockatoo has vanished from many islands and clings to survival on others.

The International Union for Conservation of Nature says as much as much as 90% of the population is thought to have disappeared since 1978, mainly due to trapping for the pet trade.

AP Video by Katie Tam & Chan Long Hei