Natural predators of the Common Swift include Eurasian Hobbies, Peregrine Falcons, Common Kestrels, Sparrowhawks and Owls (Barn Owl, Tawny Owl, Eagle Owl), although these usually only play a significant role during cold and wet periods when Common Swifts are weakened by food shortage.
The Common Kestrel (Falco tinnunculus) was and still is wrongly classified as harmless to Common Swifts, but is becoming increasingly important, especially in urban settlement areas, since it has hardly any natural enemies here, reproduces unhindered – not least thanks to human protection measures such as an oversupply of artificial nesting sites! – and has established itself as a bird hunter due to the lack of its traditional food (e.g., mice). Observations of Common Kestrels are accumulating that specifically pull young Common Swifts from their nesting cavities and even strike flying adult swifts and swallows, for which the Common Kestrel previously was not perceived as a threat. This disturbing development has so far been ignored by most ornithologists and nature conservation organizations.
In their nesting cavities, Common Swifts are sometimes killed by weasels or stone martens. House cats are quite successful at catching Common Swifts that fly low in bad weather.
The greatest enemy of the Common Swift, however – even if perhaps unintentionally – is humans, who deprive them of their basis for survival through the progressively advancing destruction of their nesting sites.