THE swift population in the London area has nearly halved in the last 10 years.

Now the Royal Society for the Protection of Birds (RSPB) is looking for help in tracking down where the birds can still be seen and where they may be nesting.

The birds, who pair for life and return to the same nest each spring from their winter home in Africa, spend most of their lives in the air.

They eat and sleep on the wing and only land to lay their eggs.

They make their nests in crevices and gaps in stonework which are virtually invisible.

The RSPB believes a loss of nesting sites through demolition and building improvements, may be the cause of their decline.

It is asking Londoners to look out for the birds and submit details of sightings and nest sites.

The best time to see them is at dusk on warm, still evenings RSPB London spokesman Tim Webb said: Once we know where they are, we can focus our conservation efforts where they will have the most impact.”