Common swifts are losing nesting cavities as old buildings are renovated, driving population decline and creating a welfare crisis for a species entirely dependent on human structures for breeding.
Swift welfare at breeding sites is acutely affected by nest site availability. A returning swift that finds its nest cavity sealed by renovation has no alternative site and will not breed that season. The welfare cost to the individual is the energy expenditure of a 10,000km migration for zero reproductive benefit. At population level, nest site scarcity creates a bottleneck that compounds the effects of food availability decline. Swift chicks are unable to thermoregulate independently and require regular feeding in an appropriate nest environment. Chicks that fall from nests require specialist rehabilitation - they cannot self-launch from the ground and will die without intervention.