A group of biologists from the University of B.C. braved army ants and driving rain to answer one simple question: What makes hummingbirds such nimble flyers?
Their research, published in the journal Science this week, examines the ways that body size, wing size and wing shape affect how the birds accelerate and decelerate, rotate in the air and make complex turns.
The deciding factor for species with the most agile manoeuvres is the capacity of their muscles to produce a lot of power, according to biologist Douglas Altshuler, who was senior author on the paper.
Wing structure matters, too.
“Their ability to make rotations was largely dictated by the size of the wings … relative to the size of their bodies,” Altshuler told CBC News.
“The complex turns were much more influenced by wing shape.”
The study is based on video recordings of over 330,000 manoeuvres performed by more than 200 birds belonging to 25 different species.
All that data produced some surprising results.
“Normally, you’d expect things that are larger to be less manoeuvrable than things that are smaller, but we actually found the opposite,” Altshuler said.
“Larger hummingbird species are more manoeuvrable than smaller hummingbird species.”
He believes that over time, these species have evolved higher muscle capacity, larger wings and advantageous wing shapes to make up for their bigger bodies.
There are big advantages to being able to turn on a dime.
Despite their fondness for nectar, hummingbirds’ primary food is insects, and their flight abilities make them pretty adept at catching critters on the wing. They can also escape predators more easily, including fast-flying raptors.
There’s also a sexual aspect to these demonstrations of aerial dexterity.
“Males often engage in very elaborate displays as they’re trying to impress females to mate with them,” Altshuler said.
Images of the birds used in the study were captured from four field sites in Costa Rica, Ecuador and Peru.
Paolo Segre, now a postdoctoral researcher at Stanford University, led the field work and had to make do under trying conditions, including rain and lightning storms. One field site was only accessible by boat, and the team’s video and computer equipment had to be operated by solar power.
“At one of the sites, they were overrun by army ants, this incredible swarm of small ants and the ants actually stayed around for two days,” Altshuler said.