Making Urban Buildings Safer for Nesting Swifts

Why Swifts Need Our Buildings

Swifts have shared our buildings for centuries, and unlike swallows and house martins they don't build nests — they need ready-made cavities. A gap under a roof tile, a hole behind a fascia board, a void beneath a gable end: these are the places where swifts raise their young. As older buildings have been repaired, repointed and sealed, those opportunities have quietly vanished.

The result is stark. Britain has lost well over half its nesting swifts in recent decades, and the birds that remain are concentrated in older, unimproved housing. Swifts spend almost their entire lives on the wing, feeding, sleeping and even mating in flight. The only time they land is to nest, which makes the loss of a single site disproportionately serious.

Protecting them isn't a job for nature reserves — it's a job for ordinary streets, and often for ordinary buildings you may already know well.

Protecting the Nest Sites You Already Have

Before you can protect a swift site, you need to find it. On warm evenings from late May onwards, look for "screaming parties" — groups of swifts racing at roof height around a particular building, often with a bird or two peeling off to slip into a gap. Watch quietly from a distance and note the exact entrance. A single hole might not look like much, but it may be the same nest used for a decade or more.

Once you know where a nest is, the priority is simply to leave it alone. Practical steps include:

• Avoid repointing, rendering or replacing tiles around an active entrance.
• Don't block a gap with insulation, soffit vents, bird mesh or expanding foam.
• Keep scaffolding clear of the entrance if any works are happening nearby.
• Remember that all wild birds' nests are protected by law while in use, and this includes swifts.
• Photograph the site and note its location so builders and future owners know it matters.

Established pairs often return to the same hole year after year, so one protected entrance can keep a small colony alive for decades.

Installing Swift Bricks and Nest Boxes

Where a site has been lost, or where you spot a suitable new building, integrated swift bricks are the best long-term solution. They're built into the wall, permanent, low maintenance and invisible from the street once finished. Position matters a great deal:

• Height: aim for at least five metres above ground, with a clear flight path in and out.
• Aspect: east, north and west walls are usually best; avoid baking south-facing spots.
• Entrance: a slot around 28mm high and 65mm wide suits swifts, keeping rain and larger birds out.
• Depth: a nest chamber of at least 100mm gives young birds room and insulation.
• Placement: keep bricks away from windows, doors and direct light, and avoid positions shaded by trees.

Cluster several bricks together rather than fitting one in isolation — swifts are colonial and readily follow each other into new sites. If a brick isn't practical, an internal nest box in a loft, with a small entrance cut under the eaves, is an excellent alternative. After installation, check that mortar hasn't bridged the entrance, and keep the hole clear of vegetation for years to come.

Reducing Disturbance During Building Works

Most swift losses happen during refurbishment, not demolition. If you're planning work on a building with known or suspected nests, timing is everything.

• Schedule roof, eave and gable work between September and April, when swifts are in Africa.
• If work must overlap the nesting season, take ecological advice before starting and be prepared to pause.
• Never use loose netting or sheeting over eaves — swifts fly fast and low, and trapped birds die quickly.
• Leave scaffold gaps clear so existing entrances stay usable.
• If a site must be lost, fit temporary boxes nearby well before the season begins.

Brief everyone on site. A short note pinned up in the site cabin, showing photos of the entrances and a named contact, prevents most accidental damage.

Making a Difference Beyond One Building

Swifts need networks, not individual boxes. A single swift brick is useful; a street of them is a colony. Talk to neighbours, your local swift group, and your council's planning department about requiring swift bricks in new developments and conversions. Many local authorities already do, and biodiversity net gain gives you a strong argument.

Keep records, too. Send sightings and nest locations to your county bird recorder or local swift group, and encourage others to look up on a June evening. Local recorders rely on these sightings to argue for protection when planning applications come forward. The more people who know which buildings matter, the safer those buildings become.