Swifts are in freefall — a 53% UK decline since 1995 driven by loss of nest sites in modern buildings. Every gap sealed in a renovation removes a nest site that swifts will search for, sometimes for years.
Swift welfare is in crisis because the urban buildings they depend on are being renovated without replacement nest provision. A swift that returns in May to find its nest hole sealed experiences displacement from a known safe site — pairs that lose nest holes may fail to breed for multiple seasons while searching for new sites. Chicks abandoned mid-development face certain death. Planning Policy Guidance in England requires architects to consider swift bricks in new builds — but enforcement is inconsistent and retrofitting remains voluntary. Swift boxes installed before renovation prevents nest site loss. The welfare case is clear and the solution is simple: maintain or replace every gap sealed.