When 14-year-old students at The ISF Academy in Pok Fu Lam helped install a nest box on their school grounds, they weren’t just building a home for Hong Kong’s iconic yellow-crested cockatoos—they were becoming part of a global lifeline for a species teetering on the edge of extinction. Once common across Indonesia, the yellow-crested cockatoo has vanished from much of its native range, with fewer than 2,000 birds left in the wild due to rampant trapping and deforestation. Yet in the heart of one of Asia’s densest cities, a population of about 200 of these striking white parrots with golden crests has quietly become a beacon of hope. A groundbreaking genomic study by researchers from the HKU School of Biological Sciences reveals that this urban flock, though small and introduced, retains genetic diversity on par with wild populations—making it a rare and vital reservoir for the species’ survival.
The findings, published in Evolutionary Applications, show that Hong Kong’s cockatoos carry genetic material from all three subspecies of the bird, including maternal lineages linked to Lombok, where the species may now be locally extinct. More than half of the birds sampled possess this lost lineage, suggesting that Hong Kong’s population could play a role in future genetic rescue efforts in Indonesia. "Hong Kong's population presents a natural, 60-year test case for the genetic impacts of interbreeding yellow-crested cockatoo subspecies," says Dr. Astrid Andersson, lead author of the study. "Instead of dismissing urban, introduced populations as ecologically redundant, we should view them as a potential 'Biodiversity Ark' that can actively help prevent extinction."
Despite their resilience, the birds face growing challenges in the city. Over 60% of their natural nesting sites—tree hollows—have been lost to typhoons and urban pruning, creating what researchers call a "housing crisis." To respond, the HKU team has partnered with schools and park authorities to install 14 specially designed artificial nest boxes across Hong Kong Island, with 10 more planned. These boxes, adapted from Australian models to withstand the city’s humidity, are equipped with internal cameras so students and scientists can monitor breeding behavior in real time. Schools like St. Louis School, Quarry Bay School (ESF), and The ISF Academy are now living classrooms for urban conservation.
While signs of inbreeding and a low number of breeding individuals remain concerns, the project is already fostering a new generation of conservationists. "Students can help build and install the nest boxes while learning about urban wildlife design," says arborist Harry Wong, a key collaborator. As the cockatoos squawk through Hong Kong’s skyline, they carry not just the echoes of a lost wild, but the quiet promise of a shared future—where cities don’t just coexist with nature, but actively protect it.