Walking by the lake on the Blickling National Trust estate, I was spellbound by a flock of seventy or so swifts. In the distance, lightning flashed while at the lake’s edge, these agile birds feasted on clouds of insects. Watching silhouettes of scythe wings and fork tails whirling over my head, I wondered if these long-distance migrants were passing through or nesting nearby. Other times, I’ve seen swifts swoop across the lake and dip their head in the water before pitching upwards and shivering to shake droplets from their feathers.

You can see swifts in Aylsham too. Sit on the grass in St. Michael’s churchyard on a summer’s evening and look skywards to see non-breeders circling in ‘vesper flights’, rising higher and higher until they disappear to sleep in the heavens. See these acrobats skimming rooftops in joyful ‘screaming parties’. Keep your eyes peeled because these birds are fast, reaching speeds up to 69 mph! In the older parts of town, if you’re lucky, you might see a swift dart under pantiles or eaves.

What do we know about these mysterious birds?

Swifts have been navigating our planet for millions of years. These unique endurance athletes feed, drink, mate, and even sleep on the wing. They rarely touch down except to rest in extreme weather and to nest in summer. Another superpower is the ability of chicks to lose heat and become torpid. This adaptation helps them cope with starvation when adults can’t find enough food in bad weather.

Much of what is known about their secret lives is documented in Dr David Lack’s Swifts in a Tower, first published in 1956 and updated by Dr Andrew Lack in 2018. This fascinating book details the long-running observational study of the breeding colony in the Oxford Museum of Natural History. More recently, with the benefit of tracking technology, much of what was deduced from observational studies is confirmed by research, in particular the aerial lifestyle of the common swift.

Swifts return to the UK from Africa in three waves

The Common Swift is the only swift that breeds in the UK, returning from Africa in late April or early May. Breeding birds, at least three or four years of age, are the first to arrive. Some will be first-time breeders that paired up and claimed a nest site last year. Although swifts go their separate ways after breeding, they return to the same nest site and pair with the same mate year after year.

Around mid-June, swifts that fledged two years ago arrive, looking for a mate and a nest site ready for next year. In the third wave, last year’s fledglings arrive looking to join a colony. It’s the non-breeding birds you’ll see in ‘screaming parties’, which are thought to help social bonding and familiarisation with local landmarks. Newly fledged swifts return to Africa almost immediately, leaving adults a little confused when they return with food to an empty nest! By August, most swifts are on their way back to tropical climates and a plentiful supply of insects.

Across the UK, we celebrate the first swifts to return home, but people are seeing fewer of these birds in their neighbourhood. Since 1995, the number of swifts breeding in the UK has declined by over 60% [BTO] and swifts are now on the UK Red List of Birds of Conservation Concern.

What are the main threats to swifts’ survival?

The main threat to their survival in the UK is the loss of nest sites, says Dick Newell, lifelong birder and founder of Action for Swifts. With their preference for dark spaces, swifts used to nest in tree holes across Europe, but deforestation has left them seeking alternative nesting places. They nest in man-made structures now, especially old buildings with displaced tiles, gaps in brickwork, and open eaves and gables. But as more and more buildings are repaired and renovated, these holes and crevices are disappearing. In 2010, swifts tagged in Eastern England travelled 14,000 miles between their departure in summer and arrival in spring, says Sarah Gibson, author of Swifts and Us. Swifts survive these epic journeys only to find their nest sites gone.

Creating permanent nest sites for swifts

Dick Newell and his team at Action for Swifts are on a mission to make more homes for swifts using their experience in engineering, construction and bird conservation. They design and install nest bricks and nest boxes for church belfries, nature reserve visitor centres, business premises, and new housing developments. Newell emphasises how easy it would be to provide ample nest sites for swifts if every new house included a low-cost nest universal brick. Swifts leave very little trace of their presence, so people need not worry about ‘mess’.

Providing permanent nest sites is the most important thing we can do to help swifts, says Newell. One swift champion is spending his retirement doing just that. So far, Suffolk-based John Stimpson has made 34,000 nest boxes, selling them at cost. With half of the boxes thought to be occupied by swifts, John may have helped 15,000 breeding pairs!

The Feather Speech advocates nest bricks in new housing

Another swift champion, Hannah Bourne-Taylor, braved the cold in Hyde Park last November, her body painted with feathers, to deliver The Feather Speech. This launched her petition to the Government to make swift bricks compulsory in new housing. A Swift Story animation explains the swift’s disappearance from our skies. Hannah’s petition has now reached the 100,000 signatures needed for a Parliamentary debate.

Plummeting populations of insects may affect swifts

However, the steep decline in swift numbers isn’t just about the loss of nest sites, says the RSPB. Swifts rely on airborne insects and spiders. The State of Nature report warns of the global decline in insect populations, which could affect all insectivorous birds. A recent study using comprehensive data finds that increased use of pesticides and fertiliser is driving bird population declines across Europe. Insectivorous birds are hardest hit.

“Birds that rely on invertebrates for food, including Swift, Yellow Wagtail and Spotted Flycatcher, have been hardest hit.” – RSPB

We don’t yet know the full impact of insecticides and the decline in habitat for insects in our countryside and gardens. In Swifts and Us, conservationist Roy Dennis laments the loss of wildflowers and insects in Scotland since the 80s when farmers began to spray crops intensively. Swifts may catch 20,000 insects a day to feed their chicks, says Sarah Gibson, so it’s a red flag that academic research shows a decrease of 49% in 15 groups of swifts’ prey between 1983 and 1997.

For now, swifts have a physiological advantage. Using a pouch in their throat, they form a bolus of invertebrates, which means they can cover long distances to hunt before returning to feed their chicks. Like migratory birds in general, as well as land-use changes and food availability, swifts are affected by extreme weather, which is becoming more frequent with climate change.

Local swift groups help local populations of swifts

Dwindling in numbers and inconspicuous by nature, swifts can be out of sight and out of mind for policymakers and the public. However, swift groups across the UK are raising awareness to secure more nest sites for these unusual yet endearing birds. Swift groups provide information on adapting soffits to create nesting places in closed eaves without access to roof spaces. They advise on nest boxes and bricks, swift call systems, liaise with local councils about planning applications, and conduct summer surveys to look for nests.

Local groups can also help with specialist rehabilitation for swifts exhausted or injured trying to access nest sites that have been closed off and for fledglings grounded when leaving the nest too early. Swift Conservation, founded by Edward Mayer, provides comprehensive resources and support to help local groups. Conservation at a local level can make a big difference to slow or even reverse the decline in swift populations in the UK. Let’s take action to help swifts in our villages, towns and cities before we lose sight of this incredible bird.

How can you help?
RSPB’s Swift Mapper shows reports by local people of nest boxes, occupied nests, and screaming parties across the UK. You might like to help with this important data collection. Is there a swift conservation group where you live that you might be able to join? If you are one of the lucky people to have these special birds nesting in your roof or cavities, let your roofer or builder know you want to preserve their nesting places.

Image credit: Two photos of swifts in flight by Julian Thomas, North East Norfolk Bird Club.
Aylsham Swift Group logo and Canva design by Tracy Brighten.