Qinghai Lake is sandwiched between Hainan and Haibei Tibetan Autonomous Prefectures in northeast Qinghai. The lake is located at the crossroads of several bird migration routes across Asia. Many species use Qinghai as an intermediate stop during migration. At its northeast end are the Bird Islands (Cormorant Island and Egg Island), which have been bird sanctuaries of the Qinghai Lake Natural Protection Zone since 1997. Every March and April, when ice starts to melt, over 20 kinds of migrating birds fly to the Bird Islands to breed. During the months, flocks of birds cover the whole sky over the islands and bird eggs can be found everywhere. The visitors can hear the warbles of birds from miles away.