Swift Factfile

The Swift is a truly remarkable bird, as it lives much of its life on the wing. Indeed, not only does the adult bird collect all its food in the air, but, outside of the breeding season, even sleeps in the air and will not land at all between leaving its nest for the last time in July or August, until it returns the following year in May having wintered in Africa. It also collects nesting material in the air (airborne materials like feathers, dry grass and seeds) and will even mate on the wing. Once the distinction between Swifts and Swallows is made – which is fairly easy as they fly very differently (the Swallow is slower and feeds much closer to the ground) and the Swift’s plumage is a uniform dark brown all over (though looks black as a silhouette) – then it cannot be mistaken for any other bird. Swifts are also characterised by their habit of flying over streets and around buildings in small groups at breath-taking speeds and emitting screaming calls as they go. Swifts will use a specific type of nest box if located in the right place.

What sound does a Swift make?

Swift nesting and breeding habits

Although the very historic location of Swifts’ nests was in cavities in cliffs, rock faces, in caves and holes in trees, it is now almost entirely in buildings – e.g. under the eaves of houses or in church towers. There are a number of key requirements for where a Swift will nest: Firstly, it needs to be in a cavity or opening which is big enough for the nest, secondly the space mustn’t get too warm (so out of direct sunlight, if, for example a special nest box is used), and thirdly it needs to be high up in the building to allow the birds to safely take off without any risk of them getting too close to the ground below (if they accidently land on the ground they find it hard to take off – and young birds would find it impossible). And lastly, Swifts are a gregarious species and therefore will look to nest in colonies – so even an otherwise perfect nest site probably won’t be taken if there aren’t others close by. The nest itself is a small cup of fine plant materials and feathers, and bound together with the bird’s saliva. Amazingly, the nest materials are gathered in the air – e.g. strands of grass and feathers which become airborne in wind. There is one brood of eggs per season with normally three in a clutch, with both parents carrying out the incubation and care of the young.

Swift history and population trends

The UK Swift population has been in serious decline certainly since the mid-1990s (probably before but the BTO’s BBS – British Bird Survey – didn’t record numbers ahead of this date), with part of the reason almost certainly being the ever-dwindling availability of suitable nest sites.

Behaviour traits of Swifts

Swift behaviour is so remarkable that it’s a worthy subject for an entire book – not just a paragraph here. However, as a brief summary of some of the really notable points: Swifts only land when they nest, and, typically, they don’t breed until they’re four years’ old. So that means that a juvenile bird leaving the nest for the first time in mid-summer, may stay airborne until the spring nearly four years later. Swifts sleep in the air (at relatively high altitude and for brief periods), entirely catch their food in the air, and adults even manage to mate in the air.

Swift diet and food

Flying insects including mosquitoes, aphids, flying ants, small beetles and hoverflies.