The rook (Corvus frugilegus) is a passerine bird belonging to the family Corvidae. It is a sizable bird, with adults typically weighing between 280 to 340 grams, measuring 44 to 46 centimeters in length, and boasting a wingspan of 81 to 99 centimeters. The plumage is predominantly black, exhibiting a blue or bluish-purple sheen when illuminated by sunlight. The feathers are particularly dense and silky around the head, neck, and shoulders. The legs and feet are black, the bill is grey-black, and the iris is dark brown. A notable feature of the adult rook is the whitish, featherless area around the base of the bill and in front of the eye, which gives the impression of a longer bill and a more domed head.
To distinguish the rook from other corvids, observe the bare patch of skin near the bill, which is absent in juveniles and other crow species. The rook's wings are also proportionally longer and narrower than those of the carrion crow when observed in flight. Juvenile rooks can be identified by their black plumage with a greenish gloss and the absence of the bare facial patch.