The rook is one of our commonest birds, and rooks are about all the year round, but they do seem rather more obvious at this time of the year. Partly that’s because our resident rooks are joined by visitors from the continent during the winter months, especially in colder years, but it’s also rooks gather in their nesting colonies long before most other birds are nesting. With the trees still bare, it makes counting our breeding rooks much easier than it can be for other birds: the bulky nests are very obvious high in the branches of tall trees.
Rooks are members of the crow family, and are distinguished from the similar-sized carrion crow by the bare grey face patch around the bill, and by the thigh feathers which look rather like scruffy trousers, as well as by their sociable habits. Rooks can form very large feeding flocks indeed at this time of the year, feeding on buried insects and insect larvae, with wireworms and leatherjackets among their favourites. These are found in greatest numbers in permanent pasture, and changes in farming practice have led to a reduction in the rook population in recent years, though it remains a common enough bird.
Rooks do cause some damage to crops, but to a degree that is balanced by their liking for insect pests. Rooks will often follow ploughs, walking behind to pick up exposed insects with a somewhat strutting gait. Rookeries are often close to human habitation, and can be noisy places as the colony gears up for another breeding season.
The nest is a bulky arrangement of sticks, many of which are apt to be stolen by neighbouring birds as the nest is being built. The male collects the materials and the female does the building, lining the cup with softer material including moss and wool. Sudden noisy and often argumentative flight displays are a feature of the nest building stage. Rooks lay up to five eggs, and the young birds are harder to distinguish from carrion crows than their parents, as they don’t at first have the bare patch around the bill; they do, however, have the scruffy trousers!
Rooks are found in every part of the UK, apart from some of the wilder parts of the far north of Scotland. I don’t see them in my garden (unlike carrion crows), but they’re never very far away, and fly over often enough to be a regular “score” on my garden bird list. Most of the rookeries I know around here are of small to moderate size, with between a dozen and say, fifty or sixty nests. Many are very old, with rooks present in a particular place for as long as any of the human residents can remember. And some colonies can develop to a remarkable size, with many thousands of nests counted in some long-established rookeries.
Rooks are among the birds shot as pests from time to time - and eaten: rook pie is a long-established country dish, usually made using young birds shot in May or June. I prefer the living bird, which for me is one of the sights and sounds which makes the countryside of Britain special.