Swifts are aerial specialists that spend most of their lives airborne, touching land only to breed, making the availability of safe nest sites in buildings the critical welfare bottleneck for this rapidly declining species.
The loss of nest sites through building renovation and modern construction is the dominant welfare threat to swifts. A swift evicted from its lifelong nest site cannot simply find another; their extreme site-fidelity means displacement often results in breeding failure and reduced survival. Chicks dying in disturbed nests or adults unable to complete their breeding cycle represent direct welfare harm from architectural changes. Building regulations requiring swift boxes in new construction in several UK local authorities represent a meaningful welfare intervention.