Breakthrough Evidence: Bats Diving After Migrating Birds
For decades, researchers have known that some bat species can hunt larger prey away from water and near the ground. A new study, however, provides compelling, direct evidence that Europe’s largest bat, the greater noctule (Nyctalus lasiopterus), hunts and eats nocturnally migrating birds in midair, high above the ground. Using high-resolution biologging tags on 14 individual bats, scientists tracked altitude, echolocation patterns, and 3D movement, revealing a chillingly efficient aerial predation strategy on a resource traditionally considered out of reach for small, winged hunters.
Methodology: How Do We Know They Hunt Birds?
The research team attached lightweight biologging devices to a sample of free-ranging greater noctules. These tags recorded altitude, echolocation calls, and three-dimensional flight paths, enabling researchers to reconstruct hunting events with remarkable precision. This approach moved beyond the indirect clues of feather debris in bat droppings and anecdotal sightings to a direct, verifiable record of a bat pursuing and consuming a bird in flight.
Atypical Hunting: High Altitude Pursuits
Contrary to the birds’ typical insect prey captures near ground level, the observed attacks began when individual bats climbed to altitudes above 400 meters. From these heights, the bats then engaged in extended, rapid downward chases, suggesting a specialized adaptation for identifying and intercepting high-flying songbirds that migrate in huge numbers at night. Each chase was lengthy and energetically costly, featuring more than 40 rapid echolocation buzzes signaling sustained pursuit of a single target.
Evidence of a Successful Kill
In one documented event, a European robin was captured and confirmed by the audio of the bird’s distress calls recorded during the attack. After capture, the bat appears to have dispatched the prey with a lethal bite and then continued to feed while still in flight. The sequence of chewing sounds, interspersed with echolocation, indicates continuous feeding for about 23 minutes without losing altitude—a remarkable display of aerial foraging stamina.
Implications for Predator-Prey Dynamics
The study also analyzed predator DNA, wing remains, and x-ray images from prey found beneath roosting sites to confirm the identity of the hunter. The data show distinctive bite marks attributed to greater noctules, supporting the conclusion that this bat species plucks, disables, and then consumes birds in flight. This aerial handling, which includes removing wings to reduce drag and simplify prey processing, parallels known aerial-hawking strategies used by some large insects-eating bats but is unusual for terrestrial birds of prey and other carnivorous mammals.
Why This Changes Our View of Bat Diets
Historically, large, mobile birds were thought to be nearly out of reach for most nocturnal predators. Yet the greater noctule’s ability to exploit a migrating-night resource demonstrates a remarkable niche specialization. The bats’ behavior highlights the complex interplay between predator physiology—such as bat echolocation and flight mechanics—and the high-energy demands of nightly migration, a period when billions of birds traverse continents. The findings illuminate how seemingly inaccessible food resources can shape the evolution of foraging strategies in aerial vertebrates.
Broader Significance and Future Questions
As researchers expand their observations, questions remain about how scalable this hunting method is across populations and seasons. Do all greater noctules regularly target migrating birds, or is this behavior concentrated in certain populations and years with especially dense bird movement? Understanding the ecological costs and benefits of aerial predation on large, agile prey will also help explain how predators balance energy expenditure with successful meals in the night sky.
Conclusion: A New Chapter in Aerial Ecology
The direct biologging evidence of the greater noctule hunting in flight marks a milestone in our understanding of nocturnal ecosystems. The capacity to capture, kill, and consume birds on wing reveals an extraordinary adaptation that has likely shaped both predator and prey behavior across Europe. As scientists continue to unravel the nuances of this predatory strategy, the night skies over Europe may be revealed as a more dynamic and interconnected theater than previously imagined.
