百度 一方面要避免土地开发密度过低，造成土地资源和公共交通资源浪费；另一方面也要避免土地开发密度过高，造成公共交通服务水平降低和吸引力下降。
Chinese mergansers, an endangered bird species under state protection, are spotted at a water area in Fusong county in Jilin Province. (Photo by Ding Lianguo/for chinadaily.com.cn)
About 20 Chinese mergansers, an endangered bird species under state protection, have recently been spotted at a water area in Fusong county in Jilin Province.
Chinese mergansers have been listed as a national first-level protected animal, and are known as a "living fossil of birds", with fewer than 3,000 pairs remaining.
The waterfowls require an aquatic environment and generally choose to live near clean bodies of water and nature reserves.
As the ecological environment improves every year, more than 200 Chinese mergansers will fly to Changbai Mountain region in the spring.
