The summer visitors worth waiting for

Few sounds say British summer quite like the screaming of swifts over a village roofline, or the liquid twitter of swallows gathered on a telephone wire before they head south. Both arrive from Africa in late April and May, and both have declined sharply in recent decades. The encouraging thing is that the two resources they struggle most to find — a safe cavity to nest in and a reliable supply of mud — are well within our gift.

This isn't about grand schemes. A swift brick set into a gable end, a tray of damp soil left in a shady corner, or a shed door left open through the season can be enough to turn a passing bird into a neighbour.

Know which bird you're helping

Swifts, swallows and house martins are often spoken of as one group, but their nesting needs are quite different, and getting this right makes all the difference.

• Swifts are the dark, scythe-winged birds that never land, sleeping and mating on the wing. They nest in dark cavities — gaps under roof tiles, behind eaves, in old wall crevices — squeezing in through a narrow slot and spending almost no time at ground level. Once a swift finds a home, it returns to it year after year.
• Swallows have a glossy blue-black back, a deep red throat and long tail streamers. They nest inside buildings — barns, stables, garages, porches — building an open cup of mud pellets and grass on a beam or ledge, lined with feathers.
• House martins are the ones with a crisp white rump. They build a closed mud cup tucked tight under the eaves on the outside of a wall, often in small colonies.

Swift bricks and nest cups

If you're building, renovating or re-roofing, a swift brick is the single best thing you can do. These are built into the wall so the nesting chamber sits flush with the brickwork, with an entrance slot roughly 30mm high and 65mm wide leading into a dark cavity. Place them at least five metres above ground, ideally on a north or north-east facing wall so the chamber doesn't overheat during a heatwave, and keep the entrance clear of obstructions.

No building work planned? A swift nest box or cup fixed under the eaves works well, and is easy to add. Points to get right:

• Height matters — five metres or more, with a clear, unobstructed flight path so birds can swoop up and stall into the entrance.
• Keep boxes out of full midday sun; a west or north elevation is usually kinder than a south-facing wall.
• Swifts are colonial, so two or three boxes side by side are more attractive than one lone box.
• Play a recording of swift calls near the boxes on May and June evenings, at modest volume. Prospecting birds are drawn to the sound of their own kind.

Be patient. Swifts are famously faithful to a site, and colonisation can take two or three summers — sometimes more. Once they're in, they tend to stay, and their offspring come back to look for homes nearby.

Mud, ledges and an open door

Swallows and house martins are limited by mud. Every nest is a few hundred pellets of damp soil carried beakful by beakful, and a dry spring can stop a pair breeding altogether.

• Leave a corner of the garden deliberately boggy, or sink a shallow tray or old washing-up bowl into the ground and keep it topped up with soil and water.
• Don't rush to fill in puddles on tracks and driveways in May and June — those roadside puddles are house martin building sites.
• For swallows, leave an outbuilding, garage or porch accessible throughout the summer, or fix a small opening high in the wall. A wooden ledge mounted about 30cm below a ceiling gives them somewhere to start.
• Keep cats away from outbuildings and nesting areas, and avoid disturbing birds that are already building.

Feed the skies

Swifts live entirely on insects caught in flight — a single bird may take thousands a day. There's little point attracting them to nest if the surrounding landscape is empty of food.

• Plant native flowers and let a patch of lawn grow long through summer.
• A small pond, however modest, raises insect numbers dramatically.
• Leave a log pile and some leaf litter undisturbed.
• Cut out pesticides and insect sprays entirely, and ask neighbours to do the same.

Timing, patience and the law

Late winter and early spring are the best times to put up boxes and bricks, so everything is ready before the birds arrive in late April. That said, anything installed at any time of year may be found later — nothing is wasted.

Once a nest is in use, leave it alone. All wild birds' nests are protected while they are active, and disturbing swifts, swallows or martins at the nest is both illegal and counterproductive. Clean out nest boxes in September or October once the birds have gone, but keep the job light — swifts often reuse the same nest the following year.

All of it, in the end, is about a summer evening: a dark shape flicking past the gutter, a chirrup from a beam in the barn, and the quiet knowledge that your bit of brick and mud made room for it.