Common Swift

The Common Swift, like all its relatives, is excellently adapted to the aerial environment it exploits skilfully. Its flight performances are extraordinary as we shall see later. It is a great migrator whose winter range is very far from its breeding range, thus carrying out very long migrations. In temperate climates, the return of the first migrants takes place around mid-April and continues until May. On the other hand, the departure at the end of summer is sudden and massive. By the end of July, once the juveniles have taken off, the great majority of swifts leave us. Some rare latecomers may still be seen at the end of August or in September, probably birds occupied with a late nest. The lifespan of the Common Swift is more than 20 years. What we mainly see of this bird in urban areas are the quick and noisy pursuits that they indulge in during the whole of the fine season around buildings. These are hard to miss out on, just like the reconnaissance flights of potential breeding sites under the roofs in accordance with an unchangeable scenario. The birds arrive with an ascending flight underneath the edge of a roof, pretend or actually land briefly while inspecting the area, take off again to come back right away.

Their manège can go on in a loop for a long time. It is the immature non-breeders who take part in such activities. Thus when they come back as adults the following year, they will probably already be paired, will have a perfect knowledge of the area and, notably, will know where to nest. As much as it is at ease when flying, it is awkward when landed. If a swift finds itself incidentally on the ground, for example after striking a wire, it finds it very difficult to take off again. Its very small legs and very large wings make it hard to take off.When not handicapped, it arrives on the bare ground, but in vegetation, it is impossible. Therefore, it must be taken by hand and thrown into the air for it to be able to fly. I have often done this without any issues with Common Swifts that have fallen into my attic or disused chimney, which I have ended up blocking off. The Common Swift's capacity for flight enables it to escape from unfavorable weather or climate conditions. This way, it can skirt around a very rainy depression or a storm zone in order to keep its ability to feed. At breeding sites, in case of prolonged bad weather, they are capable of entering a state of dormancy at the nest for several days while fasting. Their temperature decreases and they live in an energy-saving mode until favorable conditions return. It is the only group of birds to practice this kind of hibernation. Another extraordinary ability of this bird is its capability to sleep in flight without landing. One can easily observe the beginnings of this phenomenon during the beautiful summer evenings. One sees noisy Common Swift swarms rising progressively in the sky at nightfall until they are out of sight and hearing. Studies, thanks to radar among other tools, have shown that these birds remain at a high altitude, up to 2,000 meters, all night and descend again in the morning. It is assumed that they must sleep while gliding in rising hot air currents.