The Common Swift nests out of sight in cavities high up in buildings and depends on the crevices that older properties offer.
Nest site: crevices and cavities under roof tiles, behind bargeboards and in the masonry of churches, towers and older dwelling houses.
Material: the nest is simple and built from material caught on the wing — feathers, straws and seed down glued together with saliva.
Breeding: 2–3 eggs are laid deep inside the cavity and incubated for 19–20 days, well protected from weather and predators.
Since the species requires cavities in buildings it declines when crevices are sealed during renovation — specially designed nest boxes with an elongated entrance can compensate.