Birds are also (generally) smaller. > “You can drop a mouse down a thousand-yard mine shaft; and, on arriving at the bottom, it gets a slight shock and walks a

Birds are also (generally) smaller. > “You can drop a mouse down a thousand-yard mine shaft; and, on arriving at the bottom, it gets a slight shock and walks away, provided that the ground is fairly soft. A rat is killed, a man is broken, a horse splashes.” J B S Haldane https://www.phys.ufl.edu/courses/phy3221/spring10/HaldaneRightSize.pdf https://www.phys.ufl.edu/courses/phy3221/spring10/HaldaneRig... Also, of course, many birds do die.