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CATS, SPARROWHAWKS, lead-free petrol, loft insulation and cleaner streets. All of these may be factors in the staggering decline of the house sparrow.

But these are only guesses, not certainties. The real reasons for the fall of passer domesticus will not be established for another five years, scientists said yesterday.

After nearly two years of analysing 40 years of data about the house sparrow, a report funded by the Department for the Environment, Food and Rural Affairs (Defra), has painted the most authoritative picture so far of the bird's plight.

The study - which also examines the decline of the starling - concludes that there are now 10 million fewer house sparrows in Britain than there were 30 years ago. In the early 1970s, there were 12 to 15 million pairs. Now there are only six million.

The inquiry, led by the British Trust for Ornithology (BTO), has found that a large drop in survival rates for sparrows in their first year of life during the mid-1970s has played a vital role in their misfortune.

In the early 1960s, more than half of house sparrows lived to be two years old, but the figure subsequently slumped to 30 per cent. This led the population to plummet because they were failing to reach breeding age.

Since then, the sparrow's numbers have continued to decline. While the cause is still unknown, it may be as simple as the fondness cats have for chasing birds.

The report points out that the increasing numbers of people in Britain are keeping cats as pets. One study of a rural village in Bedfordshire showed that up to one-quarter of the breeding pairs of sparrows in the village may have been harmed by cats.

"Cat predation is also likely to account for a large proportion of the juvenile mortality in the village," the study said.

Cats are not the only problem. The sparrowhawk population, badly hit by DDT in the late 1960s and 70s, has returned strongly and colonised urban areas. One sparrowhawk nest in Kensington Gardens in London in 1996 was found to contain the remains of 38 sparrows.

In addition, an estimated 16,000 house sparrows were legally killed in 2001, mainly by farmers. However, that factor, which accounts for only 0.1 per cent of the population, is considered to be insignificant, the report suggests.

While the sparrow is disappearing in Edinburgh and Dublin, its sharpest decline is in London, where its numbers have dropped by 59 per cent between 1994 and 2000.

# posted by Medical Information : 3:32 AM