In high altitudes, despite the air being of low density, which makes the bird wings produce less lift and more difficult to remain aloft, high-altitude birds such as bar-headed geese, cranes, and bar-tailed godwits have been seen at high altitudes of over 6,000 metres. One possibility of how birds at high altitudes take to the air when thin air offers little lift may be simply flying faster to compensate for the lower air density. In a study published in the Journal of Experimental Biology, researchers studied if turkey vultures (Cathartes aura) residing at different elevations fly at different speeds depending on their altitude. As predicted, the researchers did find that turkey vultures do fly faster at higher altitudes to compensate for the lack of lift caused by flying in thin air. Comparing how much each bird was flapping with the different air densities, the high-altitude vultures were flapping no more than the birds nearer to sea level to counteract the effects of low air density. The high-altitude birds were likely flying faster because there is less drag in thin air to slow them down, thus compensating for generating less lift in lower air density.
