rook, term used for a common Eurasian bird (genus Corvus) of the family Corvidae (Crow family), smaller than the American crow. The jackdaw is a European species of the genus. Rooks nest in large colonies, whence the term rookery. They are classified in the phylum Chordata, subphylum Vertebrata, class Aves, order Passeriformes, family Corvidae.

Most abundant Eurasian bird (Corvus frugilegus) of the crow family (Corvidae). Rooks, 18 in. (45 cm) long, are black and have shaggy thigh feathers and bare white skin at the base of the sharp bill. They are migratory and range discontinuously from Britain to Iran and Manchuria. They dig for larvae and worms in meadows and plowed fields. They nest in large colonies (rookeries) in tall trees, sometimes within towns; the nest, solidly constructed of twigs and soil, is used year after year.

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