As they grew, their untamed nature became more apparent, though they remained notably affectionate toward long-term caretakers.

"The eight ducklings preferred moving together. In early training, they slept huddled on a man-made 'stone island' at the pool's center. Later, they delighted in bathing, gliding and hunting in the water — a charming spectacle."

Jing said the experts evaluated their growth and plan to release them later this month, adding that they believe the birds "came from and belong to nature, not the zoo".

Chen Yayun, office director of the county's forestry bureau, said the artificial nest boxes aim to provide a safe and hidden breeding space for migrant birds. They were installed at a height of between 3 to 5 meters in the forest and simulate tree holes.

More than 10 different species of birds have lived in the boxes, including owl and russet sparrow.

In recent years, large numbers of wild birds have migrated to Yuan'an to stay, nest and breed during autumn and winter.

The mandarin duck is a national second-class protected species. They have high ecological demands for their migratory habitats. In recent years, their numbers in Yuan'an have increased annually, according to local authorities.

Contact the writers at chenmeiling@chinadaily.com.cn