Sparrows sink as hawks rise

THE RETURN of the sparrowhawk is being blamed for the rapid decline of Britain's most taken-for-granted bird, the house sparrow. While the hawk's numbers have boomed, those of the noisy little quarry it is named after have slumped.

Sparrowhawks, like most other birds of prey, were victims of the widespread use of organochlorine pesticides after the Second World War. These long-lived chemicals accumulated in predators at the top of food chain, poisoning the adult birds or thinning their eggshells to the point where they broke with the embryos still inside.

But the phasing-out of DDT and other controversial agricultural chemicals since the early Seventies has transformed their fortunes. The UK population has bounced back to about 30,000 breeding pairs and now the sparrowhawk is second only to the kestrel among British birds of prey, even breeding in cities.

But Passer domesticus is not joining in the celebrations - it frequently features on the sparrowhawk's menu. The hawk, however, does not bear all of the blame for the sparrow's fall.

Many suburban sparrows fly into the countryside in winter in search of food.

There they are finding that industrial farming methods have hit their supplies. Fields of stubble strewn with spilt grain and weed seeds have largely gone due to the widespread planting of winter wheat. Crop spraying has reduced the number of insects, another vital part of their diet.

Chris Mead, of the British Trust for Ornithology, said: 'Cars and cats are also important sparrow enemies. Big picture windows seem to kill quite a large number - they sometimes fail to notice them.'

The trust's long-running winter survey has shown that over the past 24 years the average size of sparrow flocks feeding in suburban gardens has fallen from 19 to under 12. The survey is based on close observation in 200 gardens around the country.

Out in the countryside, meanwhile, the number of breeding sparrows in summer has halved since 1980.

The sparrow is not the most common British bird - wrens, chaffinches, blackbirds and robins all outnumber them - but its fondness for towns, its vulgar racket and mob-handed flocks, make it the most familiar.

It has a country cousin, the tree sparrow, which is in deep trouble. The British population of Passer montanus has fallen by more than 90 per cent over the past 25 years and now stands at about 110,000. The change from spring to autumn sowing of cereal crops has slashed its food supplies.

The British Trust for Ornithology wants to increase its numbers of official garden birdwatchers who provide it with its survey data.

Details from BTO, The Nunnery, Thetford, Norfolk IP24 2PU.