Mountain hikes are invigorating. Crisp air and clear views can refresh the soul, but thin air presents an additional challenge for high-altitude birds. “All else being equal, bird wings produce less lift in low density air,” says Jonathan Rader from the University of North Carolina (UNC) at Chapel Hill, U.S., making it more difficult to remain aloft. Mountain hikes are invigorating. Crisp air and clear views can refresh the soul, but thin air presents an additional challenge for high-altitude birds. “All else being equal, bird wings produce less lift in low density air,” says Jonathan Rader from the University of North Carolina (UNC) at Chapel Hill, U.S., making it more difficult to remain aloft. Plants & Animals Ecology Phys.org – latest science and technology news stories