It is easy to observe the behaviour of Rooks, because they always move and act in flocks. These flocks are dissolved only in cold snowy winters, when the birds, tired of the cold and lack of food, come into the villages. When the early spring ploughing begins, part of them follow the plough; the flock spreads itself over the freshly ploughed land and they snap up the grubs of the destructive insects which escape from the newly-turned clods. This then is useful work. They also settle on the sown land and pick up the seeds which the harrow has left on the surface, but at the same time devour the insects which the harrow has turned up. There is no harm in this. In a short time the full spring has come and the immature insects have developed into other forms--then the Rook begins to think of building its nest. Its young are not fed on seeds, for at that time there are none to be had, but exclusively on insects--which again is a great and useful work. Then the flock spreads over the neighbourhood, leaving their sleeping-place in the morning in a body, and betaking themselves to different parts of the district; and it may be remembered that separate flocks repeatedly visit the same spot, and work there; as, for instance, one point in a great stretch of cornland, where in the track of the birds lie many uprooted plants, which the farmer generally looks upon as due to the mischief of the Rooks. When insect life has become stronger, they settle on the meadows, where they eagerly hunt for crickets and grasshoppers; then they return to the ploughed fields and destroy the insects that have been disturbed--and this is useful work. It is true that later on they visit any heaps of cut corn that may lie in their way, and in this way do harm, but the greater number of the flock pick up the fallen grains in the stubble field, and a few follow the carts which carry the corn, and pick up any that is dropped. There is no harm in this, as these ears would in any case be lost to the farmer. At the time of the hay harvest they settle on the ridges of cut grass and hunt for crickets and grasshoppers, for these creatures have then no cover, and easily fall a prey to the birds. The Rook also attacks the young maize and fruit, but it has not skill in this respect and cannot do much harm. The harm done is outweighed a thousandfold by the good which it does in the destruction of insects. The black army of birds lights also upon the turnip crops just at the time when these valuable plants are covered with masses of the “turnip caterpillar.” By the destruction of this pest they do the farmer invaluable service.