Antwerp ZOO has successfully raised three Chinese (also known as scaly-sided) mergansers. Breeding this striking and endangered duck species is rarely successful in European zoos, making this a truly exceptional achievement.

The Chinese merganser is a cavity-nesting species found mainly along mountain rivers in China, Russia and North Korea. It migrates to Japan in winter, and is highly adapted to life underwater. ‘This duck was built for deep diving and catching fish’, explains Jan Dams, Curator of Birds at Antwerp ZOO. ‘Its bill has a serrated, saw-like edge – hence its Dutch name, which translates as “sawbill”.’

The Chinese merganser population has declined sharply, and the species is currently classified as endangered. One of the main causes is the loss of old trees, which provide the nesting cavities these birds depend on. ‘Those tall, mature trees are often the first to be felled because they’re commercially the most valuable,’ Dams says. But when the trees disappear, so do the nests. And without nests, there are no chicks.

Customised enclosure 

The global wild population of Chinese mergansers is estimated at just 500 to 2,500 birds. This makes every successful breeding attempt in a zoo all the more important. Several years ago, Antwerp ZOO made a deliberate decision to bring this remarkable duck species to the zoo. One male and two females now live together in an enclosure designed specifically to meet their needs.

‘Water quality is one of the most important factors behind our success,’ says Dams. ‘Thanks to our advanced filtration system, we can provide the birds with exceptionally clean water. It also stays relatively cool, which inhibits bacterial growth. That corresponds perfectly to the species’ natural preferences.’

Besides water quality, the design of the enclosure also plays a key role. The birds were offered suitable nesting boxes earlier this year, which were immediately accepted. A combination of environmental conditions, nutrition and species-specific care has resulted in three healthy chicks.

Valuable insights

Antwerp ZOO is one of the few EAZA-affiliated zoos – part of the network of recognised European zoos and aquariums – where Chinese merganser chicks have hatched this year. The knowledge and experience gained in the process is being shared with other zoos across Europe.

‘We compile everything we learn into best practice guidelines,’ explains Dams. ‘Which type of nest box we used, how it was positioned, what we fed the birds, how we cared for them – all of that information can help other zoos run successful breeding programmes too.’

Triplets on a mission

With an eye to a future, in which the species may come under even greater pressure in the wild, Antwerp ZOO is contributing to the conservation of the Chinese merganser through the European Ex-situ Programme (EEP). This breeding programme brings European zoos together to maintain healthy reserve populations of endangered species. In a few months, the three chicks will be sent to other zoos participating in the same programme. The aim of this partnership is to maintain strong, genetically diverse groups, so that animals can be reintroduced into the wild if needed to support the survival of the species. As the Chinese merganser population has declined sharply in recent years, there is a good chance that some of the birds kept in zoos still carry genes that have already disappeared from the wild. ‘A broad genetic base is essential,’ says Dams. ‘Species with sufficient genetic variation are better equipped to adapt to changes in their habitat – whether due to climate change or disease. Our three chicks could play an important role in this.’