Only two bird species have been seen crossing the Mount Everest, Common Crane and Bar-headed Geese.
Thousands of Bar-headed geese migrate to avoid harsh winter condition from the summer habitat of high altitude lakes where they feed on short grasses.
A few tagged geese have been observed to have flown the highest during the night time when the air density could be equal to hundreds of meter lower altitude.
Bar-headed goose can be easily distinguished by other geese by the black bars on the head as seen in the picture.
Fun Fact:
Bar-headed goose has special type of hemoglobin which helps in absorbing more oxygen in each breath it takes.