The Rook (Corvus frugilegus) is a glossy black corvid best recognised in adults by the pale, bare patch of skin around the base of its long, pointed and slightly downcurved bill — a feature that only appears between February and May in a bird's second year of life. At 44–46 cm long, with a wingspan of 81–94 cm and a weight of 280–340 g, it is roughly the same size as the Hooded Crow, but its all-black plumage carries a metallic blue-purple gloss, and loose, dense feathering on the thighs gives it a distinctive "trousered" look. Juveniles lack the bare face patch and have feathering right out to the nostrils, making them more easily confused with crows. Its call is a hard, somewhat nasal "krah-krah", drier and less harsh than a crow's, with a longer, shriller "krääääh" given in aggression, while a breeding colony produces a constant, lively din of cawing, cackling and creaking calls audible from a distance.
In Sweden the Rook is concentrated in the southern agricultural provinces, with Skåne holding by far the largest population alongside smaller numbers in Halland, Västergötland, Öland and Gotland; Sweden's largest colony is at Karlslund in northern Landskrona. The national population was estimated at around 48,000 breeding pairs in 2018 but has fallen by roughly 30 percent over the preceding twenty years, and while classed as Least Concern, the decline is being monitored. Rooks are strict colonial breeders, building stick platforms high in tree forks — sometimes barely a metre apart — from early March, with egg-laying concentrated between 1 and 15 April; the female alone incubates the usual 4–5 eggs for 16–19 days while the male feeds her, and young fledge after 29–33 days. The diet is omnivorous, dominated by earthworms, cranefly larvae and beetles probed from open fields with the long bill, supplemented by grain, seeds, nuts and berries, foraged in loose flocks over pasture and freshly sown fields.
Read about this species in Swedish →