Swift Profile

The swift (Apus apus) is a medium-sized bird with long wings and short, forked tails. When in flight, swifts appear to be black, but they are actually brown in colour. These birds may be up to 17cm in length and they boast wingspans of 42-48cm. Impressive flyers, swifts can sleep on the wing and will career in groups around rooftops at incredibly high speeds while screaming loudly. Swifts are resident in the UK during the summer months but winter in Africa.

What is the swift’s distribution and population?

Swifts are migratory birds which spend the winter months in Africa, south of the Sahara. They arrive in the UK at the end of April or in early May. They remain here only long enough to breed. Most have left by early September. Swifts can be seen throughout the UK, except for in some regions of Scotland but there are thought to be just 59,000 breeding pairs visiting the country each summer.

The swift is on the amber list of species which are of conservation concern. The dwindling population of swifts may have been caused by habitat loss and by the use of pesticides which kill their insect prey. In addition, renovation work to older buildings has removed many potential nesting sites.

What do swifts eat?

Swifts usually feed at altitudes of 50-100m. However, when wind conditions sweep insects higher, swifts will follow swarms to heights of 1,000m. These birds are selective regarding which prey to pursue, generally targeting the largest available insects. They collect their prey in pouches at the back of their throats where the insects are bound into balls held together by saliva. The balls are eaten periodically or taken to the nests. Each ball can contain thousands of insects. In poor weather conditions, swifts tend to head for water where the insects are easier to catch.

Where do swifts nest?

These birds begin to breed when they reach 4 years of age. They pair for life and meet up each year at the same nesting site. Clutches usually feature only two or three eggs which are laid at intervals of 2-3 days. Each egg is incubated for 19-20 days and by both parents. Incubation may be interrupted in cold weather as the birds will be forced to spend longer looking for food. Unusually, swift’s eggs can survive chilling and so the period of incubation is simply extended. Sometimes eggs are ejected from the nest but is unclear why swifts do this.

Swifts build their nests under the eaves of older houses and churches. Both adults construct their nest and use materials gathered in flight including feathers, paper and hay. These are cemented together by saliva. The nests are reused in subsequent years.

Did you know?

Swifts spend almost all of their lives on the wing. They sleep, drink and mate in flight and only land to nest.

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