Common swifts spend almost their entire lives on the wing, returning to the UK only to breed. The loss of nesting cavities in buildings has driven significant population declines that simple building design changes can reverse.
Swift welfare is primarily a nest site conservation issue. Swifts returning from Africa to find their nest site sealed face immediate reproductive failure and the welfare stress of fruitless nesting-site searching. Pairs that lose sites do not simply find alternatives — site fidelity is absolute and colony loss is typically permanent. Swift bricks cost around £30 and last the lifetime of a building — a trivial cost relative to the welfare benefit of supporting a colony over decades. Public engagement and planning policy are the levers — individual building owners, developers, and local authorities all have roles. The sound of screaming swifts over a town centre is an achievable conservation outcome with relatively straightforward interventions.