14 January 2000

CLEAN CROPS PLAY A PART

MANY people feel that birds of prey – in particular the sparrowhawk – are the main cause of the decline of our small bird populations. Others, including me, think agrochemicals are the major cause of small bird decline.

Nobody knows what the true population of sparrowhawks should be. They were controlled by keepers for two or three generations up to the Second World War and indirectly by dieldrin and DDT after it. When these were withdrawn, the sparrowhawks bounced back.

A lot of the problem is the way that people feed birds like blue-tits on a bird table in the middle of their gardens. If I was a sparrowhawk I would zip through gardens where birds are routinely fed – its far easier than flying through woodlands, weaving between the trees not knowing where the next bird would be. We have lured the tit family out of the woodlands or hedgerows where they normally flit from branch to branch in relative safety.

&#42 Sparrowhawk bait

The British Trust for Ornithology (BTO) monitors the population of our common birds and its figures show that farmland birds are suffering the sharpest declines. Song thrushes, grey partridges, skylarks, corn buntings, reed buntings and tree sparrows, to name but a few. But not blue tits and great tits. Even though we unwittingly use them as sparrowhawk bait, the latter have failed to dent their populations.

In 1993 I bought a farm of 44ha (110 acres) in the fens. The nearest tree was 300 yards away, so it wasnt really sparrowhawk country. The previous owner had run out of money and there was a healthy populations of skylarks.

To maintain their population, I put down three 20m x 400m grass strips with flowers in them. Each year hay has been made on the grass strips and no fertiliser has been applied, producing (I hoped) an ideal sward for skylarks. The skylarks do like them though the rich fen soil produces a grass sward that is really too thick for them.

Although the skylarks prefer the grass strips to the arable land, 2ha (5 acres) of grass is not enough to maintain their population. I grow wheat every other year with break crops of potatoes, peas, linseed, and oilseed rape. When I look in the wheat crops there are no weeds, except on the outside 6m (20ft) where I have allowed weeds to grow (except cleavers).

My agronomist has done a good job. The wheat crop usually yields around 10t/ha (4t/acre) and is too thick for a skylark to nest in. If a skylark can nest in a thin crop of wheat why cant they nest in a thick crop of wheat? We dont really know.

&#42 No central heating

If my family and I had to live in a grain store with only simple furniture and no central heating, surrounded by concrete and steel, life would be unpleasant. We could probably live there but we might not feel like or be able to raise a family. Our environment would have been altered and we could not adapt to that change. That is what has happened to the skylark; they can live in this altered environment but are unable to produce enough offspring to maintain their population.

Scavengers, meanwhile, find the modern world, with its household waste and roadkills, altogether more accommodating. We have also made nest-finding easier for them by using the flail mower far more than we need to, destroying much of the vegetation that birds could have concealed their nests in. Man is now such a dominant species on this planet, his population and activities have increased so much that several species of birds and animals have been pushed to extinction and the populations of many more are declining. A few species are able to take advantage of our actions and we dislike them for it. But sparrowhawks dont kill for the sake of it, they only kill to live. &#42

Nicholas Watts