The skylark is one of a number of farmland birds in very serious trouble. Populations of the linnet, bullfinch, reed bunting, corn bunting, grey partridge, turtle dove, and tree sparrow have also plummeted. Even common birds such as the greenfinch and yellowhammer are showing signs of decline.
We are fortunate in Britain to have a bird monitoring system that has set alarm bells ringing. Our knowledge of these trends is thanks to the efforts of many dedicated birdwatchers who take part in two surveys run by the British Trust for Ornithology (BTO). The 'Common Bird Census' has been running since 1961 and is compiled from the results gained by birdwatchers who map breeding bird territories in 100 farmland and 80 woodland plots each year.
Last year the New Atlas of Breeding Birds in Britain and Ireland: 1988-91 was published. This was the culmination of one of the largest bird surveys ever conducted. Comparison with the previous atlas, which documented breeding birds in 1968-72 shows that some species are declining in distribution as well as numbers. As yet, there is no reduction in the distribution of the skylark, but we should not be complacent. In the Thirties, the cirl bunting was widespread across much of southern England. Farming changes caused a decline in both numbers and distribution and it is now restricted to Devon. If these population declines continue at the current rate, many farmland birds could disappear from parts of Britain in the next 30- 50 years.
Pinpointing the cause of these declines is difficult. No single dramatic incident can be blamed. A series of widespread post-war changes in agricultural practice have eroded the value of the countryside for wild birds.
Farming changes, introduced by the Government since the Second World War to increase food production, have had an enormous impact on the countryside. Initially the direct loss of areas of woodland, heathland and traditional hay meadows provided startling, obvious evidence of change. However, as agriculture has modernised, there have been more subtle changes in the way our countryside is farmed and the recent decline in farmland birds is connected with these.
Lowland farms have become more specialised. Many farms no longer have a balance of arable crops and pasture and arable has become the dominant land use; the number of mixed holdings fell by 75 per cent in the Seventies.
The nature of arable land itself is changing. Most cereals are now sown in autumn which is believed to have had a significant impact on farmland birds. Ground nesting birds such as lapwing used to benefit from spring-sown cereals as they left areas of bare ground for nest sites, whereas autumn-sown crops are too dense. Autumn sowing also leads to a loss of winter stubble. The apparently bare fields were in reality full of spilt grain and weed seeds and provided a rich source of winter food for flocks of greenfinches, linnets and corn buntings.
Production methods have intensified, with widespread use of herbicide leading to a massive reduction in arable weeds. Many birds feed either directly on weed seeds or on the insects that live on the weeds. The loss of both weeds and insects therefore has an impact on birds.
Alongside changes in arable farming, grassland farming for dairy, sheep and beef production has also intensified. The area of pasture receiving nitrogen fertiliser has trebled since the Fifties, leading to a less diverse mix of plants which support far fewer insect species than old mixed hay meadows. Silage for animal feed also tends to be cut earlier, which results in ground nesting birds being killed by the mowers.
Agriculture cannot return to its Fifties production levels, but we do have enough time to stop the decline in our farmland birds. Changes in farming policies, heralded by the 1992 reforms to the Common Agricultural Policy, offer most scope for us to help birds.
Central to the new Common Agricultural Policy is the unpopular and expensive policy of set-aside. This may offer some respite for wildlife in the immediate future, however: keeping stubble unploughed in the autumn has created a vast 'bird table' covering nearly 13 per cent of arable land. In East Anglia, RSPB surveys have shown that 60 per cent of farmland finches, buntings and larks were found on set-aside land.
In future, setting aside the same land for several years should offer scope for more adventurous farming policies. But this would require a change in policy. The Agriculture Minister, William Waldegrave, should encourage farmers wishing to opt out of set-aside to choose other environmentally beneficial options - such as spring- sown cereals, organic farming or long-term habitat creation.
In the longer term, the way that farmers respond to falling prices for grain will probably determine the fate of our farmland birds. Two possibilities face us. One would be that falling grain prices would lead to less use of pesticides, herbicides and fertilisers and a greater area of land devoted to environmental schemes and returned to grassland. Alternatively, less profitable farms might go under, leaving fewer, highly intensive farms competing in world markets and offering little for wildlife.
The rules that govern farm policy must be rewritten. This is Mr Waldegrave's greatest challenge, on which rests the fate of farmland birds, farming's public image and his reputation as the greenest minister in the Cabinet.
The author is director of conservation at the Royal Society for the Protection of Birds.
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