Common swifts spend almost their entire lives airborne, only landing to breed. Modernisation of buildings has destroyed vast numbers of nest sites, causing population crashes across Europe.
Swift population collapse is driven almost entirely by loss of nest sites during building renovation. Individual swifts that lose established nest sites face repeated failed breeding attempts as they search for alternatives, causing direct reproductive failure and population-level decline. The welfare impact extends beyond individuals to whole communities of birds that return from migration to find their breeding sites gone.