The natural predators of the Common Swift include Eurasian Hobbies, Peregrine Falcons, Common Kestrels, Sparrowhawks and owls (Barn Owl, Tawny Owl, Eagle Owl), although these can usually only play a greater role during cold, wet spells, when swifts are weakened by a lack of food.
The Common Kestrel (Falco tinnunculus) was and still is wrongly considered harmless to Common Swifts, yet it is becoming increasingly significant, above all in urban areas: here it has hardly any natural enemies itself, it multiplies unchecked – not least thanks to human conservation measures such as an oversupply of artificial nesting sites! – and, for want of its traditional prey (e.g. mice), it has established itself as a hunter of birds. There are more and more observations of Common Kestrels deliberately pulling young swifts out of their nesting cavities and even striking adult swifts and swallows in flight, for which the kestrel had previously not been a threat. This alarming development has so far been ignored by most ornithologists and nature conservation organisations.
Inside their nesting cavities, Common Swifts are sometimes killed by weasels or stone martens. Domestic cats are quite successful at catching swifts that fly low in bad weather.
The greatest enemy of the Common Swift, however – even if perhaps unintentionally – is the human being, who deprives it of the very basis of its survival through the relentless destruction of its nesting sites.