Scientists Observe a High-Altitude Hunting Event as a Common Swift Falls Prey to a Peregrine Falcon.
In January 2023, scientists attached tracking devices to 8 Common Swifts in the Wadden Sea region of the Netherlands. They aimed to learn more about the birds’ annual migration to their breeding grounds in the Arctic. Everything was going smoothly until late May when one of the birds began to exhibit strange behavior.
The last photo of the tracked Common Swift. (Photo: Bloom).
Initially, Michiel Boom, a migration ecologist at the University of Amsterdam, and his colleagues noticed a sudden change in direction. While the other Common Swifts continued northwest, this particular bird flew southeast. In fact, it appeared to descend rapidly before landing on a very unusual destination for a Common Swift: a rocky outcrop. Shortly thereafter, the bird’s tracking device ceased to function. Clearly, the bird was not disoriented; it had fallen prey to a predator.
However, a closer examination of the data revealed intriguing details. Regardless of what happened to the Common Swift, the GPS signal from the tracking device indicated that the event occurred at an altitude of over 2,880 meters. This height is significantly higher than the typical altitudes at which predators operate.
Other evidence suggests this was a high-altitude hunting event. For instance, the data indicated that the Common Swift accelerated shortly before changing direction. It is likely that it spotted the attacker and attempted to escape but was unsuccessful. Additionally, when scientists recovered the Common Swift and its tracking device in Sweden, they discovered a Peregrine Falcon’s nest just 198 meters away from the site.
In a study published in the journal Ecology, Boom and his colleagues provide evidence of the highest recorded hunting event. He emphasized that predation occurs at all times on mountain slopes or plateaus. However, struggles for survival at altitudes near 3,000 meters are extremely rare. This incident may help explain why migratory birds fly at such high elevations.
For example, wading birds like the Great Snipe have been recorded flying at altitudes of over 7,000 meters. Similarly, the Eurasian Bittern can fly at altitudes of 2,377 meters above sea level at night but can reach heights of up to 6,096 meters during the day. They may be trying to avoid predators.
Two factors could make high-altitude flying advantageous for Peregrine Falcons. Large migratory flocks tend to fly at significant heights, making it beneficial for them to hunt from above. By capturing prey at such high altitudes, predators can conserve energy by flying in slow circles to a safe location.
