With all the benefits of dark plumage, why aren’t owls uniformly dark colored? Because it takes extra material and energy to produce dark feather parts, including deposits of minerals like calcium, cadmium, and zinc. (It’s not easy for owls to take in calcium—they digest the bones of their prey less efficiently than other birds of prey.) Also, darker colored feathers are heavier. The lighter colored parts of feathers weigh up to 5 percent less than the adjacent dark portions.
