A group of people are busy building bird nests for Chinese mergansers on a forestry farm at the foot of Changbai Mountain, Jilin province.

The farm is a protected area for Chinese mergansers and dozens of such birds arrive there every spring.

Two staffers from the administrative committee of the protection area hang the man-made nest which is built to look like a real tree hole. [Photo provided to chinadaily.com.cn]

Chinese mergansers often inhabit natural tree holes, but the number of trees has become less and less after years of cutting. Therefore, since 2016, man-made bird nests are prepared in the spring to offer living spaces for such birds.

The frame of the man-made nests are made of wood, in which polystyrene foam is poured to make them firm and warm. These nests must be built like real tree holes and the exits are decorated with bark from cathay poplars and lindens.

Chinese mergansers live in natural tree holes. [Photo provided to chinadaily.com.cn]

Jiang Jinsong, director of the Wildlife Conservation Association of Jilin Province, said there are about 200 mating pairs of Chinese mergansers that inhabit Jilin province. Building nests for them is significant for their breeding.

The protection area also cooperates with colleges to conduct research on Chinese mergansers' migration, breeding, habits, and living environment and has stopped actions such as hunting, firewood collection, and farming in the area to better protect the species.

Chinese mergansers are titled as "living fossils of birds" and are listed as a national first-level protected animal in China. They spend the winter in southern parts of China and return to the north in April.

Chinese mergansers are listed among the national first-level protected animals in China. [Photo provided to chinadaily.com.cn]