Common swifts are aerial insectivores that depend on holes in buildings for nesting and have declined dramatically as modern building design eliminates the cavities they require.
Swift welfare is almost entirely dependent on the availability of nest sites, which have declined catastrophically through building renovation eliminating the cavities that swifts evolved to use. Individual swifts returning to renovated buildings find their nest sites gone, having expended the energy of migration for nothing. Pairs unable to find alternative sites fail to breed, contributing to population decline that represents both conservation loss and welfare harm across a species that invests enormous energy in returning to specific sites. The solution is straightforward and inexpensive — swift bricks cost under twenty pounds and can be incorporated into any wall. Planning requirements for swift brick provision in new and renovated buildings near swift colonies create the systematic solution that individual action cannot achieve at scale.