It is known that White Eared-pheasants Crossoptilon crossoptilon drouyni interbreed widely with Tibetan Eared-pheasants C. harmani at the boundary of their ranges. A new hybrid zone has been found recently in eastern Tibet, far away from the boundary of the parental species' ranges. Based on ecological observations of eared-pheasants and the geographical history and pattern of modern glaciers, we have attributed the complex morphological variation of eared-pheasants and the high biodiversity of the eastern Qinghai-Tibet plateau to its varied geography.