Rooks are, so to speak, villaged birds. Do they roost in winter in the tree clumps where they build their nests to raise the young? A tree with old nests near Dunshaughlin, Meath, the other evening was alive with them anyway. About four o'clock, the sky clear and bluish, there were clouds of them every mile, passing towards the West.
Would you like to have a rookery on your piece of ground? Some people, it is said, pretentious it may seem, though not necessarily so, actually try to induce the birds to make one in trees near their house. (What's wrong with that?) One reader of The Field (the English one), told of a long campaign of spreading huge amounts of bread, specially bought for the purpose, as an enticement. Another writer to the same magazine - fifty years ago - told of his father's efforts in the previous century to lure them by putting up pre-fabricated nests, - sort of baskets, and how he eventually managed to encourage a colony to settle. After his day, someone cut down all the trees.
Rooks eat many insects harmful to crops, like wireworms and leatherjackets, but also feed on some farm produce such as potatoes or cereals. There are over half a million breeding pairs throughout the country, according to the expert Cabot. That evening in Meath there seemed to be thousands moving westwards into the sun, mostly.
Do they really go to roost in winter in or near the nests they used to raise their young? A writer of nearly a century ago, Marcus Woodward, believed that while nesting trees of rooks may be scattered far apart, as winter comes on they leave their summer homes to join the main army, "roosting at night in a sort of headquarters rookery."
He further states that the rooks are creatures of habit, and "it would not be surprising if it were proved that the same bird goes to roost on the same spot of the same branch of the same tree, night after night." The nest they build can be of some substance and more enduring than appears from the ground. It may have a foundation of mud or clay as ballast, bigger too than you would think from below. No wonder they come back year after year to the same construction - that is if they ever leave it. They have, writes Woodward, a strange and wonderful affection for their old homes.
He notes, too, that while you may pick up dead blackbirds, thrushes and the like in hard winters, it is not so with rooks "which well know how to look after themselves." Tough birds, and their flights lighten up a winter's evening.