Cockatoos. These birds are among the largest of the Parrot tribe, and most of them are distinguished, in a greater or less degree, by the beautiful crest of feathers on the head, which they can elevate or depress at pleasure. The name of the group is derived from the loud and distinct call-note of some of the species belonging to it, sounding like the syllables cock-a-too very distinctly uttered. They are mostly natives of Australia and the Indian Isles, where they breed in the holes of decayed trees, like many Parrots and Macaws ; they have short and powerful bills, remarkably deep at the base, and often nearly concealed by the projecting feathers of the face; the upper mandible, which is much arched, projects considerably over the lower, nearly enclosing it like a sheath; near the tip it becomes narrow and acute, the cutting edges are sinuated or toothed. The Cockatoos feed upon the seeds of various trees and plants, being able to crack the stones of the hardest fruits, they form a well-marked genus, distinguished from other groups of the Psitticinae by the above-named characteristics, and also by their light and uniform colour, which is mostly white, tinged more or less, in different species, with sulphur-yellow, or rose-red. Like the true Parrots, they have a short and even tail; and the massive and powerful bill, and robust scan-sorial or climbing feet may be taken as typical marks of their scientific classification. They do not possess the imitative powers of the Parrots generally ; their own peculiar name, or cry, being all that they are able to acquire or utter.