I’m as far from being a ‘flat-earther’ as it is possible to be, but scientific findings about nature and species do occasionally blow my mind. Sometimes facts are so astonishing that I struggle to get my head around them.  

Now we’re well into April, it won’t be long before a species responsible for one of my biggest ‘mind blown’ moments, the swift, returns for us all to marvel at. Swifts are one of our most prominent summer migrants which historically nested in crevices in cliffs. As humans morphed from hunter-gatherers into settled farmers, these adaptable birds chose to live alongside us. As people moved from countryside to towns and cities in more recent centuries, swifts moved with us, exploiting holes under eaves and between roof tiles. 

Having spent the winter as far away as Sub-Saharan Africa, swifts tend to arrive back in the UK in late April and early May. They have therefore long been a welcome symbol that summer is just around the corner. The ability of a bird that weighs about the same as two AA batteries to fly 3,000 miles (about 4,800 km) to breed here is astounding but it’s not their flying prowess that most bewilders me. Nor the fact that they can reach 69 miles per hour in level flight; their name reflecting their status amongst the fastest fliers. Miraculously, it’s also not that they rarely ever perch, landing only to nest, feed and drink – spending up to ten months on the wing.  

My awe is reserved for the fact that having evolved to do almost everything in flight, swifts can even sleep while airborne. Yes, they can sleep in the air!  Although very comfortable believing experts and trusting science, I have previously been guilty of repeating this fact without fully understanding it. Such is the capacity of nature to fill me with wonder; I accepted and shared this remarkable nugget without question. Such a marvel deserves an explanation.  Scientifically described as unihemispheric slow‑wave sleep, this complex term describes a beautifully simple evolutionary advantage. Half the brain sleeps and restores itself while the other is still awake and fully functional. 

Whereas humans tend to be stumbling and barely functioning when half asleep, swifts can fly and navigate – giving a whole new meaning to ‘sleeping with one eye open’. This ability helps them complete their long migrations more quickly and keeps them safe from predators. 

Sadly, whilst the swifts’ choice to live amongst humans once served them well, more recently, it has contributed to a dramatic decline in numbers. Modern buildings don’t offer the nooks and crannies swifts rely on for nesting. For every ten swifts that soared in our skies 30 years ago, the RSPB says that only three would likely be counted today. 

Having shared our homes for millennia, heralding the arrival of summer and showing such extraordinary skills, swifts deserve more attention and support. Thankfully, perhaps inspired by our long association with these birds and the joy their annual return brings; a growing movement of people across the UK – including here in Notts – is determined to help turn things around. 

‘Swift Streets’ are being created where residents install specially designed swift boxes under their eaves to tempt these much‑loved visitors back. Some Swift Streets involve dozens of residents and hundreds of nest boxes. Many have been inspired by the remarkable efforts of John Stimpson, who single‑handedly built more than 30,000 swift boxes – providing enough swift real estate to accommodate half the swifts that visit our shores. 

Here in Nottinghamshire, WildNG are leading the way, supporting Swift Streets in areas such as Sherwood and Carrington and organising an inspirational Swift Homecoming Parade each spring to highlight the birds’ plight, engage local children and encourage communities to rally behind these special birds. 

So, when you spot or hear your first swift of the season high above your street, don’t just marvel at the incredible journey it has made or see it as a sign that summer is on its way. Spare a thought as to whether it will find a place to nest or has travelled 3000 wasted miles! If you can, install a box so they can share your home for the few short weeks they’re with us.