Swifts, the fast-flying summer visitors which are among Britain's most extraordinary birds, are being renovated out of existence.
Their traditional nesting places in roofs and eaves are rapidly vanishing as older houses and other structures are upgraded – while newer buildings, especially those in steel and glass, provide no space whatsoever.
Edward Mayer, who is campaigning to have nest boxes installed on buildings and to have the species' plight recognised, warns that eventually there will be no nesting places left.
Surveys by the British Trust for Ornithology (BTO) have shown a dramatic fall in swift numbers between 1995 and 2005, with a decline of 22 per cent in England and Wales and a 38 per cent fall in Scotland.
Swifts come from Africa to breed in Britain every year and stay for the shortest period of any migrant – arriving in May and leaving as early as mid-July. Their distinctive arrowhead silhouette in the sky is seen by many people as a symbol of summer.
Like the swallow family – which they superficially resemble, but to which they are unrelated – they have adapted to human habitation, squeezing through the gap under the eaves of houses, churches, hospitals and town halls to nest typically on the beam on which the roof rafters rest, where they are safe from predators. But the way is being barred. Many buildings erected after the Second World War do not have such gaps and, as the older housing and building stock is renovated, nesting opportunities are disappearing all over Britain. Recent buildings, especially in modern materials such as steel and glass, are a swift no-go area. This has resulted in the tumbling numbers, says Mr Mayer.
The retired senior civil servant is mounting a vigorous campaign to draw attention to the swifts' plight and to popularise the introduction of nest boxes, which can be mounted outside buildings and which the birds will use once they realise they are there.
He would like swift nesting places to receive official protection locally and nationally in the same way in which legal protection is given to bat roosting sites, which cannot be disturbed and must be replaced with similar spaces elsewhere if they are.
"Loss of nest sites is causing a catastrophic loss of this species, a species that moved from a wild to a human habitat – and now humans are destroying the human-created habitat," said Mr Mayer, 60.
He gives a prime example of how the birds can be induced to nest in artificial colonies – the tower of Oxford University's Museum of Natural History, where since 1948 swifts have used nest boxes. This year about 70 pairs are breeding in the tower, watched over by amateur ornithologist Roy Overall, as they have been for the past 46 years.
Despite having had a hip replacement, Mr Overall, 76, regularly scales the ladders which lead to the top of the tower, where the birds nest in boxes behind the ventilation openings.
His knowledge of swifts' lives is encyclopaedic – from their ability to sleep, and even mate, on the wing, to the chicks' ability to endure hunger and cold for far longer than other birds.
*Details of Edward Mayer's campaign can be found at www.londons-swifts.org.uk