How hummingbirds switch gears at breakneck speeds

Some of the fastest and most agile birds are hummingbirds. They can obtain nectar in tiny areas and fly at 9Gs while courting without hurting themselves.

Their flight appears to be regulated. Hummingbirds employ two sensory techniques to fly, depending on whether they are moving or hovering. The findings were reported in Proceedings of the Royal Society B on January 10.

Hummingbirds use a “internal forward model” to fly. This automatic model lets them gauge speed despite multiple visual inputs.  

“There’s just too much information coming in to rely directly on every visual cue from your surroundings,” research co-author and University of British Columbia zoologist and comparative physiologist Vikram B. Baliga said.  

The birds employ more real-time, direct sights from their environment when hovering or managing indications that require them to shift altitude, the scientists found.  

The scientists introduced 11 wild adult male Anna's hummingbirds (Calypte anna) into the lab to analyze flight patterns. They asked the birds to fly from a perch to a feeder in a 13-foot tunnel and videotaped each flight.  

To investigate how hummingbirds responded to different visual stimuli, the researchers projected patterns on the tunnel's front and side walls.

To simulate forward momentum, researchers projected vertical stripes flowing at different rates on the tunnel wall in particular flight conditions.  

Other times, horizontal stripes on the side simulated altitude. Team projected whirling swirls on front wall. Circular patterns were used to simulate position shift.

Baliga added, “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.” In response to the patterns, the birds changed velocity or stopped, although there was no clear association.