Why swifts need a helping hand
Swifts are among the most exhilarating sights of a British summer. Their screaming parties, tearing across the rooftops on long sickle wings, are the soundtrack to warm evenings from May to August. Yet these remarkable birds are in serious trouble. The UK swift population has fallen by more than half in the past twenty-five years, and a shortage of nesting sites is a major reason why.
Swifts are cavity nesters, traditionally tucking themselves into gaps under the eaves of old houses, churches and barns. As buildings are renovated, soffits are sealed and roof spaces are blocked up, those opportunities vanish. A well-placed nest box on your own home can genuinely make a difference — but swifts are fussy tenants, and getting the details right is what separates a box that sits empty for years from one that rings with the calls of hungry chicks.
Choosing and siting a swift box
Position is everything. A swift box needs to be
at least five metres above the ground, and higher is better. Swifts enter their nest by dropping into the entrance from above, so they need a clear, unobstructed flight path for several metres in front of the box. If trees, wires or a nearby wall get in the way, they will simply look elsewhere.
Aspect matters too. In the UK, the ideal orientation is
north, north-east or north-west. These aspects avoid the fierce afternoon sun that can turn a shallow box into an oven, cooking eggs or chicks during a heatwave. A spot that catches the morning sun but is shaded later in the day is perfect.
You also want shelter from prevailing wind and driving rain. An exposed gable end facing the south-west may look ideal from the ground, but swifts will avoid a box that takes a battering. Look for a recessed wall, a sheltered corner, or a spot under a deep eave.
Other practical considerations:
- Fix the box directly to brick, stone or timber — not to fragile render or cladding.
- Keep it away from windows and doors where disturbance is frequent.
- Mount it as high as you safely can, ideally just below the roofline or under the eaves.
- If you have several boxes, group them. Swifts are colonial and are far more likely to move into a site where others are already nesting nearby.
The importance of timing
When you install your box matters enormously. Swifts arrive back in the UK from early May, having flown from central Africa without landing once. They are tired, they are ready to breed, and they are looking for a ready-made home. A box that appears in June is a box that has missed its window.
The best time to put up a swift box is
autumn or winter, so it has weathered in and is waiting when the birds return. Failing that, aim for
March or early April at the very latest. If you are installing one now and it is already mid-season, do not despair — put it up anyway, because young non-breeding swifts prospect for nest sites in late summer and may remember your box for next year.
Timing also applies to the birds themselves. Swifts typically fledge in August and leave by the end of the month. Once they have gone, the box sits empty for nine months. Do not assume it has failed — that is simply the rhythm of a swift's year.
Making your box irresistible
A swift box is not simply a box. The entrance should be a
narrow oval or star-shaped slot, roughly 30 millimetres high and 65 millimetres wide, which keeps out larger birds while letting swifts slip through. The interior should be deep and dark, with a shallow concave floor to hold the eggs in place. Avoid anything with a large open front, as starlings and sparrows will claim it first.
One of the most effective tricks is
playing swift attraction calls. A small speaker placed near the box, playing recordings of swift screams at dawn and dusk through May and June, can draw prospecting birds in. The sound tells passing swifts that this is an active, safe colony site. Do keep the volume modest and switch it off at night so you do not disturb your neighbours.
Aftercare and patience
Once your box is up, resist the urge to check it constantly. Swifts are sensitive to disturbance at the nest, and a box that is opened during the breeding season may be abandoned. If you want to monitor, use a small endoscope camera or a nest box camera fitted permanently, and keep inspections to the winter months.
Clean the box out in
October or November, removing old nesting material and any parasites, then leave it alone until spring. Do not apply insecticides or strong-smelling treatments inside.
Above all, be patient. Swifts are long-lived and fiercely faithful to their nest sites, returning to the same box year after year. A new box may sit empty for two, three or even four seasons before a young bird claims it. But once swifts take up residence, they tend to stay — and the scream of a swift party around your own roofline is one of the great rewards of a British garden.
Oliver Radcliffe
