The calls of swifts overhead are, for me, the sound of summer arriving — joyful, nostalgic, but now tinged with sadness. Once one of Britain’s most familiar summer sounds, the common swift has lost more than half its UK population since 1995.

• Feb–Apr: Northbound coastal route via West Africa
• Jul–Oct: Autumn inland route south

Each spring, common swifts make a near‑14,000 km round trip from sub‑equatorial Africa to UK skies. Northbound, they hug the West African coast through Liberia and Senegal, cross the Sahara on tailwinds, and arrive over Britain in late April and early May. By August they slip away again on a more inland track, over the Congo Basin and into Mozambique, spending the next eight months almost entirely on the wing.

• Typical season
• vanguard
• peak
• departure

The first vanguard birds typically reach southern England in the last week of April, with the main population arriving across the UK through the first ten days of May. Departure begins almost as soon as the young have fledged: adult males slip away from mid‑July, followed by females and then juveniles. By mid‑August most swifts have gone, with stragglers seen into September, a UK season of barely a hundred days.

Britain’s swifts are disappearing. We’ve lost about 70% of them since 1995, and the decline isn’t slowing, with numbers down 26% in just the last five years. They’ve now joined house martins and cuckoos on the UK’s Red List of at-risk birds.

The drivers are complex, but experts point to two main pressures. The first is housing: modern building standards and renovations are sealing up the old roof cavities and gaps under eaves where swifts have nested for generations. The second is food. Britain’s flying insects have collapsed in number, and swifts depend on them entirely, eating nothing else across their long summer on the wing.