What look like tangled lines of abstract art are actually the result of time-lapse photography of the dizzying flight patterns of the common swift (Apus apus) taken in Barcelona, Spain, in June 2019. “Every morning and afternoon they join in groups to fly in circles or chase each other. They have many different flight behaviors; that's why it’s one of my favorites birds to work with,” says photographer Xavi Bou, who took the shot as part of a long-term project called Ornithographies. The aim of the project is to make these otherwise invisible flight paths visible to humans. From their breeding grounds across Europe and Asia to their wintering grounds in Southern Africa, the dark brown birds capture food and material for their nests while airborne. In fact, a 2016 study in Current Biology that attached small sensors that measured movement to several swifts in Sweden showed that they stayed aloft for 99 percent of their 10-month nonbreeding season. The finding raises the possibility that common swifts sleep while airborne, as some other bird species have been shown to do. Swifts can also live up to their name: a 2010 study in the Journal of Avian Biology clocked one bird flying at 69.3 mph, the fastest on record for any bird during level flight. The species seems to turn on its turbo drive during “screaming parties,” a social display where they swoop and circle and make high-pitched calls to each other.

Science in Images