Ten Months Aloft: Study Reveals Common Swift's Unprecedented Aerial Endurance

Groundbreaking scientific findings have confirmed the extraordinary stamina of the Common Swift (*Apus apus*), demonstrating its capacity to remain airborne continuously for a staggering ten months. This remarkable feat was meticulously documented by a research team led by Professor Anders Hedenström from Lund University in Sweden. The study, which appeared in the journal Current Biology back in 2016, sheds significant light on the unique evolutionary adaptations that allow this bird to sustain a near-total life lived in the air.

The investigative team utilized miniature data loggers attached to thirteen individual swifts to track their movements. These sophisticated devices incorporated accelerometers to record activity levels and light sensors to precisely determine geographical location. The resulting data analysis revealed that, outside of their breeding season, these birds spend over 99.5 percent of their existence aloft. Swifts sustain themselves by catching insects mid-flight and are believed to utilize the sky for sleeping during their extensive migratory journeys spanning from Northern Europe down to Central Africa. They only touch down on solid ground for approximately two months annually, dedicating this time exclusively to nesting activities in their northern breeding grounds.

The Common Swift's short legs render it particularly vulnerable to terrestrial predators, a factor that likely reinforces the necessity of remaining airborne for such extended periods. Researchers are now intensely focused on deciphering the precise physiological mechanisms that permit these birds to enter a state of sleep without interrupting their continuous flight patterns. Key adaptations include the ability to enter a state of torpor, similar to a coma, when faced with cold temperatures or food scarcity. This metabolic slowdown allows them to conserve vital energy. While adult swifts can sustain this torpid state for up to two days, juveniles are capable of surviving in this condition for as long as five days.

The Common Swift ranks among Europe's fastest avian flyers. When maneuvering in groups over their established territories, colonies can achieve dive speeds approaching 220 kilometers per hour. Only a few other species surpass this speed in a dive; the White-throated Swift (*Apus melba*) reaches 250 km/h, and the Hobby falcon (*Falco subbuteo*), which is also a natural aerial predator of swifts, can hit 240 km/h. Young swifts, having fledged in late July, display flight proficiencies comparable to adults and, critically, never return to the nest site after leaving.

This comprehensive investigation effectively validated a hypothesis first proposed by Welsh ornithologist Ronald Lockley back in the 1970s. Swifts exhibit remarkable fidelity to their nesting locations, consistently returning to the same colonies around May 1st in Central Europe. Furthermore, breeding pairs often maintain their bond across multiple years. During the nesting phase, when pairs are occupied with incubation (typically laying two to three eggs) and raising their young, they continue to fly until deep into the night. These findings underscore that flight is not merely a behavior for the swift, but the very foundation of its existence, demanding peak metabolic efficiency, which is supported by features like a four-chambered heart and a highly efficient double-breathing system.