Napahai Lake Nature Reserve is both an ideal grazing field for herdsmen and a paradise for many species of birds. This is, in the true sense, a seasonal lake. When summer comes, snow on the adjacent mountains melts and flows down into about ten rivers forming a vast lake. In the dry season, Napahai becomes a boundless green grassland–the best time for herding sheep or cattle. Every September, the lake again turns into a temporary habitat for migratory birds, such as bar-headed geese, wild ducks and black-necked cranes (one of the 12 rarest bird species in the world). During this period, the lake becomes an ideal place for ornithologists from around the world.