THE humble house sparrow has been crowned Lancashire's most popular garden bird -- but spotting one is more difficult then ever.

Fears about the little bird, distinctive for its dowdy plumage and speckled breast, has prompted a study to discover the reason for its decline.

And it is not the only bird in trouble -- the common starling has also suffered a dramatic drop in numbers.

The figures were revealed in the Royal Society for the Protection of Birds' 26th Big Garden Birdwatch.

An average of 3.7 sparrows were spotted in gardens across Lancashire, compared to a national average of ten in 1979.

Starlings were second with an average of 3.58 spottings, compared to 26 years ago.

The Big Garden Birdwatch was conducted by 8,800 people in Lancashire in January when they were asked to spend an hour counting birds in gardens, schools or local parks.

The declining number of sparrows has earned the bird a place on the RSPB's 'red list', which denotes species needing urgent help, and the RSPB has launched its own study.

Jim Bonner, of Blackburn and District Bird Club, said: "I think it has something to do with the lack of nesting sites. Sparrows used to nest in the eaves of houses but modern homes are all sealed so the birds cannot get in.

"We are just starting a project to display sparrow nesting boxes to see if it will help increase the numbers in the area. Of course, other experts have their own theories, such as lack of food and environmental changes.

"The drop in starling numbers could well be the same thing, a lack of nest sites. They used to nest in chimneys and could be a nuisance. But modern homes do not have chimneys."

RSPB Big Garden Birdwatch aims to find the most common seen garden birds as an indicator of the health of the environment.

Co-ordinator Kirsten Whittaker said: "Big Garden Birdwatch allows hundreds of thousands of people to get involved with a project that tells us how some of our best loved birds are faring.

This sort of survey enables the RSPB to understand more about the population trends of UK garden birds."

Another change giving cause for concern is the song thrush.

After a slight increase, their numbers have dropped in 2005, and for the first time the red-listed species dropped out of the top 20. It was seventh in 1979.

The most widespread species this year was the blackbird, recorded in 92 per cent of gardens, with house sparrows and starlings seen in 68 and 53 per cent of gardens, respectively.

And blue, great, and long-tailed tits all continue to prosper in the UK.