Photo taken on March 31, 2020 shows migrant birds at the Wolong Lake wetland in Kangping County of Shenyang, capital of northeast China's Liaoning Province. (Photos: Xinhua)

Photo taken on March 31, 2020 shows migrant birds at the Wolong Lake wetland in Kangping County of Shenyang, capital of northeast China's Liaoning Province.

Photo taken on March 31, 2020 shows migrant birds at the Wolong Lake wetland in Kangping County of Shenyang, capital of northeast China's Liaoning Province.

Photo taken on March 31, 2020 shows migrant birds at the Wolong Lake wetland in Kangping County of Shenyang, capital of northeast China's Liaoning Province.