
A whooper swan is seen in Gahai Lake wetland in Luqu County of the Tibetan Autonomous Prefecture of Gannan, northwest China's Gansu Province, June 2, 2021. Gahai Lake wetland on the Qinghai-Tibet Plateau has become home for some endangered migrant bird species over the years thanks to its improving ecological environment.Photo:Xinhua

Bar-headed geese are seen in Gahai Lake wetland in Luqu County of the Tibetan Autonomous Prefecture of Gannan, northwest China's Gansu Province, June 2, 2021. Gahai Lake wetland on the Qinghai-Tibet Plateau has become home for some endangered migrant bird species over the years thanks to its improving ecological environment.Photo:Xinhua

Bar-headed geese are seen in Gahai Lake wetland in Luqu County of the Tibetan Autonomous Prefecture of Gannan, northwest China's Gansu Province, June 2, 2021. Gahai Lake wetland on the Qinghai-Tibet Plateau has become home for some endangered migrant bird species over the years thanks to its improving ecological environment.Photo:Xinhua

A black-necked crane is seen in Gahai Lake wetland in Luqu County of the Tibetan Autonomous Prefecture of Gannan, northwest China's Gansu Province, June 2, 2021. Gahai Lake wetland on the Qinghai-Tibet Plateau has become home for some endangered migrant bird species over the years thanks to its improving ecological environment.Photo:Xinhua

Aerial photo shows black-headed cranes in Gahai Lake wetland in Luqu County of the Tibetan Autonomous Prefecture of Gannan, northwest China's Gansu Province, June 2, 2021. Gahai Lake wetland on the Qinghai-Tibet Plateau has become home for some endangered migrant bird species over the years thanks to its improving ecological environment.Photo:Xinhua