Where have all the sparrows gone? That's the question the RSPB is asking the next few days as part of a nationwide house sparrow survey.

The once common chirpy house sparrow was added to the charity's red list of birds for conservation concern last year.

Their numbers plummeted by a staggering 64 per cent between 1972 and 1996 with an estimated loss of 9.6 million birds a figure equivalent to the human population of Scotland, Wales and Northern Ireland.

During the past year much has been said about their plight and a number of theories, including lack of food and lack of nest sites have been put forward, but there's still no obvious explanation for the recent decline.

Emma Foulger, Wiltshire RSPB's community officer, said: "This is the first RSPB house sparrow survey to take place and we are asking people to count the number of house sparrows in their area between now and Saturday and record that information on our survey form.

"It doesn't matter whether you live in the middle of Swindon or in one of the surrounding villages. We need to build up a comprehensive picture of where sparrows are successful and where they aren't, so even if you don't see any, we want to know about it!"

It may seem surprising to say but house sparrows are in trouble

But studies over the last 25 years have shown that their population has more than halved.

In urban areas, this decline seems to have been even more dramatic a fact confirmed by the London house sparrow survey last year.

Some of the theories for this decline are:

n the lack of food in the wider countryside due to more efficient farming methods

n the lack of nest sites modern buildings offer sparrows fewer opportunities

n development of derelict land may have reduced food availability

n the increased use of pesticides in the countryside and gardens may reduce the numbers of insects which sparrows need to feed their young.

Emma added: "With your help, we aim to find out more about house sparrow numbers. The first step in any conservation action is to collect information.

"We need to know where house sparrows are doing well and where they are doing badly.

"Because house sparrows live near us, we are asking you to count your local sparrows when they are most active."

To take part in the survey, you will need to study the birds in your garden over a day period. This can be today, Friday or Saturday.

Answer the questions on the form opposite and send it to the address printed on it.

We will publish the results in the summer.