Distribution and migration
Swifts breed throughout Europe as far north as Lapland and the Arctic Circle, reaching east across Asia to China. They show no preference for particular ground-level habitats but they do require insect food in the air, preferably at heights over 50 m and a suitable nest site nearby.
Swifts traditionally nested in crags, sea-cliffs, caves, hollow trees and nest holes made by other birds. These sites have largely been replaced by nesting in buildings, which has allowed the swift to colonise many new areas, including cities, throughout its world range.
In more recent decades the application of pesticides and habitat destruction may have had adverse effects on swifts by affecting their food supply. The modernisation of many buildings has resulted in loss of nesting sites.
Swifts are migratory throughout their range. They arrive in the UK in the last week of April or early May, and stay only long enough to breed. Autumn migration begins in late July or early August. The onset of the migration is believed to be triggered by the lack of nutritious insects high in the air. Few swifts are left in September.
Our UK swifts migrate through France and Spain to spend their winter in Africa, south of the Sahara, where they follow the rains to take advantage of rapid changes in insect populations. While many immature birds return to the breeding grounds in the spring, some will remain in Africa.
The world population is estimated at around 25 million birds.