Vintage Bird Wallpaper

There is, of course, a considerable difference between the speed at which a bird can fly and the speed at which it normally does fly. When the bird is "around home" one might expect it to do one of two things, minimize its energy use per unit time, that is, minimize its metabolic rate, or m e the distance it travels per unit of energy expended. A vulture loitering in the sky in search of prey might, like the pilot of an observation aircraft, maximize endurance; a seabird traveling to distant foraging grounds might, like a Concorde encountering headwinds on a transoceanic flight, maximize range. Staying up longest does not necessarily mean going farthest. A bird might be able to stay aloft 6 hours at 15 mph (maximum endurance, covering 90 miles) or 5 hours at 20 mph (maximum range, covering 100 miles). Birds can also choose to maximize speed, as when being chased by a predator or racing to defend a territory. Or they can choose some compromise between speed and range