Eagles are large birds of prey which are members of the bird order Falconiformes and family Accipitridae, and belong to several genera which are not necessarily closely related to each other genetically. Most of the more than 60 species occur in Eurasia and Africa. Outside this area, just two species (the Bald and Golden Eagles) can be found in the USA and Canada, a few more in Central and South America, and three in Australia. Eagles are differentiated from other birds of prey mainly by their larger size, more powerful build, and heavier head and bill. Even the smallest eagles, like the Booted Eagle, which is comparable in size to a Common Buzzard or Red-tailed Hawk, have relatively longer and more evenly broad wings, and more direct, faster flight.
Most eagles are larger than any other raptors apart from the vultures. Like all birds of prey, eagles have very large powerful hooked beaks for tearing flesh from their prey, strong legs, and powerful talons. They also have extremely keen eyesight to enable them to spot potential prey from a very long distance. This keen eyesight is primarily contributed by their extremely large pupils which cause minimal diffraction (scattering) of the incoming light. Eagles build their nests, called eyries, in tall trees or on high cliffs. Many species lay two eggs, but the older, larger chick frequently kills its younger sibling once it has hatched. Eagles are sometimes used in falconry. They appear prominently in myth and literature. In the Old World, such references are commonly to the Golden Eagle.