Introduction to the Pure Water Bird: On the banks of glacial lakes such as Dayehai, there is a small bird with a black back, a red belly and a white top, called the white-crested brook robin. It chirps and flies quickly, sometimes skimming the water, and sometimes It stands among the rocks and picks up the grass and twigs on the water surface to prevent the lake from being polluted. People call it a water-purifying bird.