Distribution of birds in the high-altitude area of Mount Everest

INTRODUCTION The Himalayas includes the world’s highest peak,Mount Everest(8848 m),and the altitude gradient of the southern slope of the mountain range changes rapidly,from Mount Everest to 100 km south,with the habitat shifting from glaciers to tropical rain forests at altitudes below 1000 m.This area is a global hotspot for bird distribution(Orme et al.2005),and the area is home to one of the highest concentrations of threatened birds in Asia.(Acharya&Vijayan 2010).Bird diversity research in this area has revealed that the eastern Himalaya mountain range,south slopes,and mid-lower altitude areas have higher levels of bird diversity than the western Himalaya mountain range,north slopes,and high-altitude areas,respectively(Acharya et al.2010,2011;Price et al.2011;Wang et al.2013;Romanov et al.2016).In addition,the adaptability of birds to high-altitude areas,such as the enhancement of the oxygen transport capacity of the Barheaded Goose(Meir&Milsom 2013)and changes in the flight characteristics of vultures(Sherub et al.2016)have also been investigated.However,most of these studies were carried out at altitudes below 5000 m.For the mountain range with the highest peak,at 8848 m,there are very few studies on the birds in large areas above the snow line,and bird data at very high altitudes mainly come from the sporadic records of early climbers(Swan 1961,1970).