Swift Information

Bristol Swifts website aims to provide a range of practical information and advice about swifts and what can be done to help them.

The Common Swift (Apus Apus) is the most aerial of all birds and spends most of its entire life on the wing, flying continuously day and night. In its lifetime a bird may fly a distance of some 4 million miles, which is equivalent to flying to the moon and back again eight times. A swift only lands after 2-3 years where it returns to the general location of its birth to find a mate and raise its own family.

For many the sound of a “screaming party” of swifts is the quintessential sign that summer has finally arrived. They can be quite frenetic at times, like screaming little black demons, hence their old-fashioned name ‘Devil Birds’. We might think of them as a British bird, but in fact they only spend about three months with us, arriving in late April or early May to raise their young and leaving by early August. The remaining nine months are spent in Central and Southern Africa.

After a 6000 mile journey back from Africa, they can be seen gathering first over Chew Valley and Blagdon Lakes near Bristol. There they feed up on the newly hatched flies that have emerged from the water in their millions. Once they have regained their strength after a few days they start to return to their traditional nesting locations. This is summed up beautifully in Ted Hughes poem ‘Swifts’

They’ve made it again,
Which means the globe’s still working, the Creation’s
Still waking refreshed, our summer’s
Still all to come

Swift breeding cycle

Clutch normally 2-3 white eggs (May-June)

Incubation period 19-21 days (mostly  hatching mid June)

Fledging is 5-8 weeks (late July-early August)

One year old  birds return in July to suss out colonies, but don’t stay long and never start nest building.

Two year old birds arrive from mid May onward to look for a suitable nest site, find a mate and begin nest building.

Three year old birds return in early May to breed for first time.

Swifts are almost entirely dependent on our buildings for their nesting sites, squeezing into small nooks and crannies generally under the roof tiles or soffits. Unfortunately when older buildings are refurbished these little openings are often inadvertently sealed up by the homeowner and the nest sites are lost forever. To make matters even worse virtually all new buildings are extremely wildlife “unfriendly” with no spaces available for birds to nest.

If a few nooks and crannies are left open or swift nest boxes installed, either internally or externally, swifts will have a place to nest. Swifts increase the colony size by moving to adjacent areas. So if there are no swifts spotted either nesting or in screaming parties in the area then it may be difficult to attract them. This is a major consideration when siting new nest boxes.

swift box designs


Swifts are extremely site faithful, so once they have found a suitable nest site they will continue to use it for the rest of their lives. Some colonies are very old indeed and have been used by successive swift generations for tens if not, hundreds of years. Their dependence on our buildings makes them very vulnerable to any sort of disturbance, so once a colony has been destroyed it makes it very difficult for them to find a new home and a whole breeding season can be lost forever.

Trying to find swift nest sites is not easy. They fly so quickly that they can be very difficult to locate. If you are trying to find an existing swift nest site then here is a link with a few tips.

Swifts numbers are declining for a variety of different reasons, but one that all the experts can agree on, is the lack of suitable nest sites available to them. Like so many other small birds, swift numbers have declined sharply in recent years. Between 1995 and 2018 their numbers have fallen by as much as 58%. Such a decline has led to the species being Red-listed in the fifth Birds of Conservation Concern report, and classified as Endangered in the second IUCN Red List assessment for Great Britain.

Perhaps you want to help maintain a local colony or maybe try to attract swifts to nest at your own property? Whatever it is we can offer you some advice and guidance.

Copyright © 2024 Mark Glanville. All Rights Reserved.