Common swifts are in serious decline across Europe, with a 40% population fall since 1995 driven primarily by loss of nesting opportunities in modern buildings.
The decline of swifts represents both a conservation loss and a welfare concern: a species adapted over millions of years to aerial life is losing its one non-aerial dependency — breeding nesting sites. Birds that fail to find nesting sites cannot breed; those evicted from existing sites during building renovations lose nest attempts with energetically costly consequences. Each swift that survives migration from sub-Saharan Africa only to find its natal nest site bricked up experiences a welfare impact as real as any captive animal denied its behavioural needs.