He has recorded over 60 species of birds.

"It's all because the water is cleaner. No one is pickier about the environment than the birds," he said.

During his rounds, Han saw several hundred ducks of different species, including Chinese spot-billed ducks and mallards.

"I did not see as many different species before 2017," he said.

Han also takes students with him, hoping to show them that their area is home to all kinds of beautiful birds.

"They need to get to know the birds first, and then they will become aware that they need to protect them, especially when they see how beautiful they are," he said.