Nest boxes help Hong Kong’s yellow-crested cockatoos

On a humid afternoon in September, conservationist Harry Wong climbed a tall candlenut tree at a school in downtown Hong Kong, fastened a nest box to it and rappelled back down. Two teenage boys watching from below compared him to a superhero. Wong and Astrid Andersson, a biologist and postdoctoral researcher at the University of Hong Kong, run HK Cockatoo Watch, a project that protects the city’s feral yellow-crested cockatoos.

The yellow-crested cockatoo is critically endangered, with fewer than 2,000 birds left in its native range in eastern Indonesia and Timor-Leste. Few people know that Hong Kong holds the largest wild population outside those two countries: roughly 200 birds, or about 10% of the global wild total. They are believed to descend from released or escaped pets, and their number is stable because the city has no natural predators for them and the species is strictly protected by law.

A recent DNA study by Andersson’s team found that Hong Kong’s cockatoos have unexpectedly high genetic diversity, which means they could help save the species from extinction in Indonesia.

City life is still hard for them. Cockatoos normally nest in tree holes, which are plentiful in Southeast Asian rainforests, but in a city they cannot count on finding such holes. That is where the artificial nest boxes come in, giving the birds a place to breed and giving researchers a chance to study their behaviour.