RESEARCH, some conducted in the North, has highlighted the perilous position of the house sparrow.

National figures show that the population has fallen from 12 million pairs in the 1970s to no more than seven million today.

But the research, by the British Trust for Ornithology (BTO), has thrown up a mystery because the bird appears to be producing plenty of young.

The ornithologists discovered that breeding performance - the number of chicks per nesting attempt - has increased throughout Britain in the past 40 years with the most rapid improvements in the north and west.

Despite the increase, the population has continued to fall and the BTO believes the reason is chicks' inability to survive their first year.

The research suggests that the reason in the countryside is changes in agricultural practices but that the situation is more complex in urban areas, where 60 per cent of house sparrows live.

It is calling for extra research into possible causes including predation by domestic cats and sparrowhawks, loss of weed seeds caused by zealous gardening, and poor air quality.

The report was written by BTO researchers Humphrey Crick, Rob Robinson and Graham Appleton and commissioned by the Department of the Environment, Food and Rural Affairs.

"Who would have guessed that the familiar 'chip, chip, chip' of the house sparrow would start to be missed by many householders across the country", says the report.