Visitors take photos of Brown-headed gulls flying over the Pangong Tso Lake on June 14, 2021. (Photo: China News Service/ Ran Wenjuan)

A Brown-headed gull wanders by the Pangong Tso Lake on June 14, 2021. (Photo: China News Service/ Ran Wenjuan)

Brown-headed gulls fly above the Pangong Tso Lake in southwest China's Tibet autonomous region, June 14, 2021. (Photo: China News Service/ Ran Wenjuan)

A group of Brown-headed gulls cruise on the Pangong Tso Lake in southwest China's Tibet autonomous region on June 14, 2021. (Photo: China News Service/ Ran Wenjuan)

A Brown-headed gull prepares to peck food fed by a visitor on June 14, 2021. (Photo: China News Service/ Ran Wenjuan)