The mystery of the rooks' evening procession

 

Another Life:The quiet of autumn falls from one day to the next. Suddenly my trainers are thumping and scuffing loudly on the early-morning march down the boreen. The narrow lane is muffled in flowers, brilliant thickets of loosestrife, meadowsweet, montbretia: purple, foamy ivory, hot orange, writes Michael Viney.

No longer paced along the ditches by vigilant stonechats and linnets, I find crows in meditative charge of the hillside. On one side, six solemn ravens on a fence-post each. On the other, a dozen jackdaws line the roof-ridge of a not-quite-finished bungalow. Yesterday, they chose a different roof: an empty holiday house nearer the sea. I suspect them of scouting (if not actually emerging from) all the new nest-sites offered by unguarded, unused chimney-pots (a wildlife survey for someone?).

I still miss the rooks. Well, in one way, not at all: for years they plundered my potatoes, arriving in what a neighbour called "the green dawn" to rifle my ridges, stabbing holes in the biggest potatoes and carrying the "po-eens" off whole. They came from a farm down the hill, an old house sheltered in a spinney of arching syacamores. When the rooks were nesting - about 50 pairs - the daily clamour and droppings must have been insupportable, so the final eviction came as no surprise. How many rectors and priests, I wonder, maddened by the din of their ancient rookeries, have chafed at the impossibility of taking up a gun?

Ireland has been good to rooks. In fact, at some 520,000 pairs, they are Ireland's most widespread birds, nesting almost everywhere (Co Derry has the highest density). Back in the 1980s, an ornithologist friend, Ron Macdonald, did his PhD on rooks and, in 100 sq km of Co Kildare, counted 66 rookeries with close on 5,000 nests. He also used something called, magnificently, a GallenKamp automatic adiabatic bomb calorimeter, to discover that one acorn (another autumn harvest for rooks, who cache them in the fields) is equal in energy to about 30 small earthworms.

He and Mark Cocker would have got on well together. The latter's new book, Crow Country (Jonathan Cape, £16.99), is as obsessive a celebration of rook and jackdaw - and of human immersion in nature - as anyone could wish.

Cocker's devoted observation of birds has run through half a dozen fine books, most recently the encyclopedic Birds Brittanica he wrote in association with his fellow naturalist in Norfolk, Richard Mabey. Cocker moved with his family to a rundown cottage in the Broads and became entranced by the twice-daily flight-lines of rooks and jackdaws passing over the house. Tracking their course at dusk - "scattered like patterns of iron filings across the metallic sky of winter" - he found some 40,000 crows gathered on the banks of the river near tall woods of ivy-covered oaks. As the light faded, their assembly fell almost silent and sifted more closely together into a mass of black. Then came the ritual, mysterious drama that has taken over so much of his life: the piecemeal eruption of the flock in a thunderous roar of ascending wings and calls, blossoming "as an immense night flower" over the woods before twisting down into the trees to roost.

The evening processions of rooks to their wintertime roost has already produced some memorable writing, from John Clare onwards. Like Cocker, Richard Jefferies, in the 19th century, was intrigued by the origin of the crows' routes back and forth: "It is possible that the line taken by the rooks indicates the line of the first clearings in very early days." But while Jefferies could find "weird oppressiveness" in the passage of wings - like "a vast invisible broom sweeping the sky" - Cocker is tireless and exhilarated by his evenings out on the marsh in winter, counting rooks and jackdaws as they stream overhead.

His quest has been to know why they do it - that is, why they find it worthwhile to spend perhaps an hour of each short winter day flying, at some 42km an hour, to get to and from their roosting togetherness. His mission has taken him on long journeys in Britain, to uncomfortable vigils, for little reward.

Indeed, he can offer no radically new conclusions. The initial push into roosting "could be protection from predators or the elements, or its function as a food- information centre". Or all of these, of course, and more besides. Still, monitoring 45 separate rookeries, Cocker doesn't expect to have all the answers, perhaps ever, and is perfectly happy with that.

The search for meaning in his own obsession - why does he do it? - inspires some of the best insights of Crow Country. Among them is his rediscovery of the magic of winter dusks in the countryside, when blackbirds chink, wrens make a last dash between hedges, and pairs of rooks go whiffling down into the dark.

Eye On Nature

At noon we saw a bat circling a ruin on Inchagoill Island in Lough Corrib, then landing on the wall, where we were able to stroke it. Aren't bats nocturnal?

Barbara Browne, Knockmore, Co Mayo

Bats will come out during the day, if need be, when feeding young. The wet summer would have made foraging difficult.

We are organic gardeners and recently our land is infested with New Zealand flatworms. In the polytunnel I find them under growing pots, which I use as traps to destroy them. But how do I deal with them in the open ground?

Marliese Hertfelder, Ballyhaunis, Co Mayo

Set traps by weighing down plastic sacks in damp areas. Destroy worms by burning, squashing or immersing in salty water. Black eggs are produced in summer. Juveniles are creamy white/pink.

I lifted a piece of decayed timber in my garden to find a black lizard. Do they hibernate at this time and what would explain its smoky black appearance?

John Morris, Spiddal, Co Galway

Lizards hide under objects when not foraging. Their colour is variable, with numerous black spots and males darker.

Michael Viney welcomes observations at Thallabawn, Carrowniskey PO, Westport, Co Mayo, or viney@anu.ie. Please include a postal address