This section is from the book "The Balance Of Nature And Modern Conditions Of Cultivation", by George Abbey. Also available from Amazon: The Balance Of Nature And Modern Conditions Of Cultivation.
The Rook (Corvus frugilegus), Fig. 32, included in the sub-family of the Corvinae or true Crows of Conirostal Insessors, possesses its distinctive characters in the base of the bill being naked, as well as the forehead and upper part of the throat, which parts in the Crow are feathered, though in the young rook feathers exist at the base of the bill, but these disappear when the bird is a month old. The wings of the rook are long and somewhat rounded, so that it is capable of long flight and performing sundry evolutions in the air. Its colour is black with a bluish sheen, and the length of the bird is 19 in.
Rooks are gregarious, and in autumn and winter have particular roosting-places, where they congregate in vast numbers in a certain wood, and include the scattered broods for a considerable distance around. In the early spring or late winter they pair and repair, in part to new or former nesting-places, such as a grove of trees near a house, or in a park, or by a church, and in small woods, frequently near the habitations of man. The nests are built on the tops of high trees, and are composed of sticks or twigs, lined inside with dead grass and other material, old nests being repaired. The eggs are five in number, and are bluish green, with dark spots or patches. The male and female sit alternately upon the eggs, and both attend to the rearing of the young birds. This occurs during the spring, usually April, when insect larvae are equally voracious with the nestling rooks. Cockchafer grubs, wireworm, leather-jackets and other ground pests of crops, oak-leaf roller moth caterpillars, small ermine and other moth caterpillars, with slugs and worms, form a major portion of the food of the young rooks and of their parents.
But the rooks also feed upon newly sown grain, upon "set" potatoes, and are oftentimes a great plague to poultry and pheasant rearers, not only taking the food, but in some cases appropriating weakly young birds. For walnuts the rooks have a particular penchant, taking them off the trees wholesale, and they act similarly in regard to acorns, feeding also upon beech-mast, wild berries and various seeds.
Fig. 32. - The Rook.