Rook, a European bird closely related to the crow of North America. The rook grows to about 19 inches (48 cm) long. It has black plumage with a purple gloss, and black feet, legs, and bill. A bare, grayish-white patch surrounds the base of its bill. Its voice is like that of the crow. Like the crows, rooks are bold and intelligent. They are the most numerous birds in England.
Rooks nest in tree tops in large colonies, or rookeries, that often number a thousand birds or more. The nests are built of twigs lined with straw. From three to five blue eggs blotched with brown are laid in early spring.
Rooks destroy vast numbers of insects, but they also devour huge quantities of grain. It is questionable whether they are more useful than destructive.
The rook is Corvus frugilegus of the crow family, Corvidae.