the evening, the birds often congregate at their rookery before moving off to their chosen communal roosting site. Flocks increase in size in autumn with different groups amalgamating and birds congregating at dusk before roosting, often in very large numbers and in the company of jackdaws. Roosting usually takes place in woodland or plantations, but a small minority of birds may continue to roost at their rookery all winter, and adult males may roost collectively somewhere nearby. The birds move off promptly in the morning, dispersing for distances of up to . Large groups of rooks (in breeding colonies or night roost sites) can contribute to changes in soil properties. The amount of ornithogenic material in these soils is very high. Foraging mostly takes place on the ground, with the birds striding about, or occasionally hopping, and probing the soil with their powerful beaks. Flight is direct, with regular wingbeats and little gliding while in purposeful flight; in contrast, the birds may glide more extensively when wheeling about in leisure flight near the rookery. In the autumn, flocks sometimes perform spectacular aerial group flights, including synchronised movements and individual antics such as dives, tumbles and rolls. Diet and feeding Examination of stomach contents show that about 60% of the diet is vegetable matter and the rest is of animal origin. Vegetable foods include cereals, potatoes, roots, fruit, acorns, berries and seeds while the animal part is predominantly earthworms and insect larvae, which the bird finds by probing the ground with its strong bill. It also eats beetles, spiders, millipedes, slugs, snails, small mammals, small birds, their eggs and young, and occasionally carrion. In urban sites, human food scraps are taken from rubbish dumps and streets, usually in the early hours or at dusk when it is relatively quiet. Like other corvids, rooks will sometimes favour sites with a high level of human interaction, and can often be found scavenging for food in tourist areas or pecking open garbage sacks. Rooks have even been trained to pick up litter in a theme park in France. Courtship The male usually initiates courtship, on the ground or in a tree, by bowing several times to the female with drooping wings, at the same time cawing and fanning his tail. The female may respond by crouching down, arching her back and quivering her wings slightly, or she may take the initiative by lowering her