Few birds have such ambivalent relationships with humans as swifts. On the one hand, the progressive destruction of habitats and food resources, an increase in the lucrative trade in "Edible Bird"s Nests" – the nests made of saliva by Southeast Asian swiftlets – and the use of insecticides and herbicides have become a serious threat to many swift species. On the other hand, many species benefit as synanthropes from an abundant supply of nesting sites on human buildings and plantings, e.g., palms.
Of the approximately 94 species of Apodidae, six have been included in the Red List of the International Union for Conservation of Nature (IUCN), including significantly five swiftlets of the genus Collocalia. Overall, the endangerment of species in the family is below the average of just over 10% of endangered bird species worldwide (STATTERSFIELD and CAPPER, 2000).
The Common Swift is one of the bird species that has spread very rapidly to high northern latitudes in historical times following humans (GLUTZ and BAUER, 1980). Originally breeding in the wild, where it used tree cavities and rock crevices as nesting sites, it found almost ideal breeding conditions in human cities: nesting sites protected from predators and equally well insulated from cold and heat in walls and gables of tall buildings. In some regions of Southern Europe, nesting sites were even specifically created for it – albeit not unselfishly: towers with access to the nests, from which the brood was removed, killed and eaten towards the end of the nestling period, leaving only one young (BREHM, 1922). The original natural breeding sites lost their importance for the Common Swift almost completely; today there are only a few tree-breeding colonies – in Germany, for example, in the Selke valley.
But this initially sensible "evolutionary opportunism" is leading to a growing threat for the Common Swift in the present. In their choice of nesting site, the species that breeds exclusively in Europe has now become completely dependent on humans. However, during building renovations and roof work, more and more sites for old swift colonies are being destroyed and sealed off, partly deliberately, partly out of pure ignorance. On the one hand, especially in Western Europe, the trend towards a hostile, sterile metropolis is progressing rapidly, and in renovations as well as new buildings, possibilities for animals that once lived with humans are hardly ever considered. On the other hand, the Common Swift finds it extraordinarily difficult to develop new breeding sites, preferring instead to return undeterred for years to the familiar nesting site.
Therefore, it is to be feared that without active conservation measures, these still common birds, which have enlivened the summer evenings of our cities with their flight games and calls for centuries, will disappear from the urban landscape as unstoppably as they once conquered it.