Common swifts are declining across Europe due to loss of nesting sites in renovated buildings and declining aerial insect populations, with significant welfare implications for this remarkable long-distance migrant.
Swift welfare is inseparable from their remarkable lifestyle — animals that spend 99% of their existence airborne face welfare threats concentrated in the brief period when they land to breed. Loss of nesting sites through building renovation strikes at this single land-based vulnerability. Breeding failures caused by site loss result in pairs returning year after year to attempt to enter sealed buildings, sometimes attempting entry repeatedly before moving on — or sometimes not finding an alternative and failing to breed that season. The welfare harm of nest site loss extends across decades for long-lived birds with strong site fidelity. The aerial insect decline compounds this by reducing food availability. Swift box installation is a concrete, individual welfare action that directly replaces lost nest sites — a rare conservation intervention where a single homeowner can make a measurable welfare difference.