The white-headed eagle is three feet long, and seven feet in extent; the bill is of a rich yellow; cere the same, slightly tinged with green; mouth flesh-coloured; tip of the tongue, bluish black; the head, chief part of the neck, vent, tail coverts, and tail, are white in the perfect, or old birds of both sexes, in those under three years of age these parts are of a gray brown; the rest of the plumage is deep, dark brown, each feather tipt with pale brown, lightest on the shoulder of the wing, and darkest towards its extremities. The conformation of the wing is admirably adapted for the support of so large a bird; it measures two feet in breadth on the greater quills, and sixteen inches on the lesser; the longest primaries are twenty inches in length, and upwards of one inch in circumference where they enter the skin; the broadest secondaries are three inches in breadth across the vane; the scapulars are very large and broad, spreading from the back to the wing, to prevent the air from passing through; another range of broad flat feathers, from three to ten inches in length, also extend from the lower part of the breast to the wing below, for the same purpose; between these lies a deep triangular cavity; the thighs are remarkably thick, strong, and muscular, covered with long feathers pointing backwards, usually called the femoral feathers; the legs, which are covered half way below the knee, before, with dark brown downy feathers, are of a rich yellow, the colour of ripe Indian corn; feet the same; claws blue black, very large and strong, particularly the inner one, which is considerably the largest; soles, very rough and warty; the eye is sunk, under a bony, or cartilaginous projection, of a pale yellow colour, and is turned considerably forwards, not standing parallel with the cheeks, the iris is of a bright straw colour, pupil black. The male is generally two or three inches shorter than the female; the white on the head, neck, and tail being more tinged with yellowish, and its whole appearance less formidable; the brown plumage is also lighter, and the bird itself less daring than the female, a circumstance common to almost all birds of prey.