Lewes Swift Supporters

Because Swifts spend most of their lives flying through the air they can be difficult to study! There is still a lot that even the Swift experts do not know about them - but what they do know and share is fascinating!

Did you know?

• The habitat of Swifts is in the air! Swifts feed, drink, sleep, and sometimes even mate, on the wing and only land when they are ready to make a nest! In early May you may see them flying as a pair then plummeting together as they mate.
• We usually hear Swifts before we see them. They are famous for their "screaming parties" and are known to respond to calls from other Swifts. Hear the Swift call by visiting this RSPB fact page about Swifts. 
• Their wing spans are 42-48 c.m., or 16-19 inches, and their wings are able to move both forwards and back. Their short take-off, high speed turns and extreme agility have been studied by aerodynamic engineers to inform developments in aeroplane technology.

These photographs, above, from Jonathan Pomroy and Robert Booth, show the specialised feathers, called "alulae" sticking up from the wing surface. They correspond to the slots of aeroplanes that increase lift and manoeuvrability at low speeds, (Swift Conservation). the first photograph show how Swifts can use their forked tails as a rudder.

                                                               Swifts prospecting and entering a nest box in Valence Road

• Swifts have been recorded as living for as long as 20 years and are extremely faithful to their mates and their nests. Less than 10% of Swifts are not monogamous, possibly because their mates fail to return from migration to Africa, (source RSPB June 2026).. Inadequate legal protection for their nests during the months when they are not occupied is a threat to existing colonies.

Photograph by Nick Jarvis of two chicks in a nest box in Valence Road, August 2025

• Unlike Swallows and House Martins, there is usually no visible sign of a Swift nest from the street - most of those we find in Lewes are hidden under the eaves. Our surveyors rely on seeing entrances and exits to record active nests. An advantage of occupied nest boxes is that you can often see the Swifts at the entrance later in the season - as shown in the photograph above! 
• Once a fledgling leaves the nest, it will be flying constantly before touching down to breed in its fourth Summer. It is estimated that they fly over 14,000 miles each year! They can fly for up to four days without food or water because their aerodynamic design needs little energy to power their flight. 

Swift flying back to the nest with nesting material caught in the air, Robert Booth.

• Swifts line their nests with any suitable items they can catch as they fly through the air, sticking it together with saliva. Sometimes they even nest on a bare surface. Gillian, one of our Supporters who has up to eight nests at her home, found cobwebs, a small piece of tissue, a fragment of grey and white feather and part of a feather boa amongst the fallen debris from one of her nests. Swift nests should never be removed!

Swifts and egg in an old Sparrow's nest in an attic in King Henry's Road

• Incubation of Swift eggs takes 18-21 days and both parents share the incubation duties. The chicks are ready to fledge after 37-56 days, depending upon the weather and availability of insects. During cool periods, the chicks can go into a period of torpor until the weather improves. When the chicks are almost ready to fledge, they practise "press-ups" in the nest to build up their strength before their first flight.
• Parent Swifts feeding chicks need to catch about 20,000 insects and airborne invertebrates a day. They collect them in a special pouch at the back of their throats and bind them together with saliva, then carry this back to the nest and regurgitate them for the chicks. Each ball of food, (bolus), can contain up to 1,000 insects! They mostly feed on "aerial plankton" such as flying ants, aphids, mosquitoes and spiderlings - but their largest prey is though to be a Hoverfly. They also eat drone Bees which do not have a sting - they can recognise them as drones because they fly at a different altitude and make a different noise. 
• It used to be thought that Swifts flew through the air with their beaks open to catch airborne insects and invertebrates. Edward Mayer dismissed this idea at his recent talk for Lewes Swift Supporters, ( May 2026), pointing out that this would make them less aerodynamic and prone to dehydration. He reports that they open their beaks to catch each individual insect. The gape of their beak is almost as big as their head!

Swift carrying a bolus of food - by David Moreton, by kind permission of swift-conservation.org

This photograph by Ulrich Tigges show the deep-set eyes of the Swifts, surrounded by dark bristles called rictal bristles or vibrissae. These stiff feathers reduce glare and act as both an insect-catcher and a protective shield against wind and airborne debris as they fly at high speeds.

• Swifts have been recorded as flying at a speed of up to 70 m.p.h. and at heights of up to 5,700 metres, (18,700 feet). They have been recorded as flying from Morocco to Cambridge in just two days!
• Although more research into sleeping Swifts is needed, it is widely believed that Swifts can shut off half of their brain so that they can fly and sleep at the same time!
• Swifts are not related to Swallows and Martins - they belong to the same bird family as Hummingbirds, Apodidae, and are near relations to the South-East Asian Tree Swifts.
• Swifts sometimes fly through the rain to have a wash! They can skim low over the surface of water to gather a few drops to drink. This is a very dangerous exercise because if they misjudge and become wet they are likely to go under the water and be caught by a fish. They can also drink by catching raindrops!

• Our Swifts winter in Sub-Saharan Africa - the Congo basin, Zimbabwe and Mozambique. Migration flights from tagged birds have been recorded as 12,400 to 17,000 miles - the longest migration for a land bird. They fly to Europe to breed because, compared to the Tropics, we have a longer day length for feeding in Summer. This is essential so that they can catch all the insects that they need to feed their young.

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• Most of the Swifts we see in Lewes are Common Swifts. Their scientific name is Apus apus, from the Greek word for "without feet". Because they are flying for much of their lives, in ancient times it was thought that they had no feet! Their feet are further back on their bodies than most birds so they cannot walk easily. They have no "thumb" and all four of their toes point forward so that they can cling to a wall, rock face or a tree trunk and their claws are very sharp. Although they cannot walk on the ground easily, a healthy bird is able to take off from the ground - as we have seen in Western Road when a Swift fell to the ground after a tussle in a nest!
• Swifts used to nest in holes on cliffs or in old Wood[pecker nests in trees, (and still do nest in trees in Poland, Scotland and Sweden), but now largely rely on human habitation for nest sites. They are thought to have been nesting in human's buildings since Roman times. Nest entrances have been recorded, for example, under pantiles, in holes in walls, under soffit boards, in broken air bricks, eaves or in louvred ventilation tiles. This makes them highly vulnerable to renovation and house maintenance!

Swift nesting in a tree, by Olle Tenor

Thanks to Edward Mayer of Swift Conservation for many of these interesting facts.There is a lot more to find out about Swifts on the brilliant Swift Conservation website: swift-conservation.org

Or you might like to read:

• "Swifts in a Tower" by David Lackey
• "Swifts and Swallows" by Mike Unwin, RSPB Spotlight series
• "Vesper Flights" by Helen MacDonald
• "On Crescent Wings" by Jonathan Pomroy, (fantastic paintings!): jonathanpomroy.wordpress.com
• "Swifts and Us" by Sarah Gibson 
• "Screamer the Swift" by John Miles and Barry Robson - also available as a video on YouTube
• "One Midsummer's Day - Swifts and the Story of Life on Earth" by Mark Cocker
• "The Screaming Sky" by Charles Foster

For younger readers:

• "Swifts" by Lorna Hill
• "Swifts - Mysterious, Prehistoric, Endangered" by Helen Lucy, (available from Lewes Swifts Supporters)