Hummingbirds have astounded scientists once again with their remarkable flight abilities. Recent research conducted by zoologists at the University of British Columbia (UBC) has revealed that these tiny birds employ two distinct sensory strategies to govern their flight, depending on whether they are hovering or in forward motion. Dr. Vikram B. Baliga, the lead author of the study published in Proceedings of the Royal Society B, explains the fascinating phenomena, stating, "When in forward flight, hummingbirds rely on what we call an 'internal forward model'—almost an ingrained, intuitive autopilot—to gauge speed. There's just too much information coming in to rely directly on every visual cue from your surroundings."
However, when hummingbirds are hovering or confronted with cues that necessitate a change in altitude, they rely more heavily on real-time, direct visual feedback from their environment. This discovery not only provides insights into how these agile birds perceive the world during flight transitions but also has the potential to contribute to the development of navigation systems for future autonomous flying and hovering vehicles.
To unravel the secrets behind hummingbird flight, the researchers devised a series of experiments. Hummingbirds were observed performing repeated flights from a perch to a feeder in a four-meter tunnel. The team projected various visual stimuli onto the chamber's front and side walls to gauge the birds' reactions. Each flight was meticulously recorded on video for analysis.
The researchers projected vertical stripes moving at different speeds on the side walls to simulate the sensation of forward motion. Horizontal stripes were employed to mimic changes in altitude. On the front wall, rotating swirls were projected, creating an illusion of altered position.
Dr. Baliga explains the rationale behind the experiments, stating, "If the birds were taking their cues directly from visual stimuli, we'd expect them to adjust their forward velocity to the speed of vertical stripes on the side walls. But while the birds did change velocity or stop altogether depending on the patterns, there wasn't a neat correlation." Interestingly, the hummingbirds displayed a more direct response to stimuli indicating a change in altitude during flight. Moreover, during hovering, the birds meticulously adjusted their position in response to the shifting spirals projected on the front wall.
Dr. Doug Altshuler, the senior author on the paper, highlights the unexpected findings, stating, "Our experiments were designed to investigate how hummingbirds control flight speed. But, because the hummingbirds took spontaneous breaks to hover during their flights, we uncovered these two distinct strategies to control different aspects of their trajectories."
The implications of this research extend far beyond our understanding of hummingbird flight. These findings could profoundly impact the development of navigation systems for next-generation autonomous flying and hovering vehicles. By integrating the sensory strategies employed by hummingbirds, engineers may devise more efficient and adaptable flight control systems.