One of Britain's favourite birds could be under threat from a new airport development in South Africa.
The swallows migrate to South Africa during the British winter
The Royal Society for the Protection of Birds (RSPB) says swallows which migrate south during winter may lose a traditional roosting site near Durban.
An airport is planned to be built there before the 2010 Fifa World Cup.
The swallows could end up beneath the flight path and there are fears the reedbed will be cleared, because the birds could threaten aircraft safety.
Swallows fly south to their winter roosting sites in South Africa and Namibia at this time of year.
One area that attracts them is Mount Moreland Reedbed in the province of Kwa-Zulu Natal, just north of Durban.
It is the size of four football pitches and is thought to host more than 3 million swallows.
The reedbed is also believed to be a home to more than 8% of the swallows breeding in Europe and is also used by lesser kestrels, corncrakes and crowned eagles, all of which are now uncommon.
An environmental impact assessment is being conducted but the RSPB says that regardless of the La Mercy international airport development and the plans for the World Cup, this site is crucial for the swallows.
Paul Buckley, head of global programmes at the RSPB said: "The loss of Mount Moreland and with it thousands of British swallows could be felt from Thurrock to Thurso and Sofia to Stockholm.
"It would be devastating for these birds, which are particularly sensitive to change.
"Swallows are one of Britain's favourite birds, they are an icon of spring and epitome of summer.
"But developments undertaken without good environmental protection as far away as Kwa-Zulu Natal may trigger their long-term decline right here on our doorsteps."
Drought and pesticide use on the swallows' migration route, added to the conversion of farm buildings and other favoured nesting sites, have resulted in a decline of the birds' population in the UK.