Watch Tanya Mercer's report
A pensioner in Cambridge has built 27,500 swift boxes in attempt to prevent further decline in numbers of the beloved bird.
Admired for their aerial acrobats that adorn summer skies in the region, the numbers of swifts are rapidly declining.
Numbers have halved in the last 25 years as home owners improve their homes making it harder for the birds to nest.
Swifts return every year to their exact nesting sites, so when these are destroyed so too is the swifts' chance to breed.
But John Stimpson is hoping to change that. Over the last 25 years, he has turned his garage in his home in Wilburton into a swift box factory - dedicating his retirement to making thousands of swift boxes.
Swifts spend their whole life in the air - feeding, drinking, mating and sleeping on the wing.
The only time they land, is to breed.
They're the fastest bird in level flight reaching speeds of 70 mph and can fly up to 10,000 feet high.
Every year they travel between Africa and Europe. Some will fly up to 1.6 million miles in their lifetime - the equivalent of flying to the moon and back 7 times.
To go through such a journey and then not be able to nest is what drives John on to make so many boxes.
John's boxes have gone all over the UK, to France, Spain, Italy, Luxembourg and Sweden.
It's estimated he's made enough to house a third of the UK's swift population and he hopes to reach 30,000 boxes by his 80th birthday in January.