Video of a purple-crowned woodnymph shows "snap-buckling" beak. (Gregor Yanega)
The shape of a hummingbird’s beak enables a "snap-buckling" mechanism for capturing flying insects, according to a new study to be published in the Journal of Theoretical Biology.
Hummingbirds cannot survive solely on floral nectar; they need to hunt for insects to sustain themselves, and the beak’s unique structure allows the birds to be omnivores.
"Hummingbirds need the equivalent of 300 fruit flies a day to survive," said co-author Gregor Yanega at the National Evolutionary Synthesis Center in Durham, North Carolina, in a press release.
Yanega’s previous research on hummingbird beak anatomy using high-speed videos showed that the bendy lower beak flexes by as much as 25 degrees when it opens, creating a larger surface area for trapping insects.
But Yanega noticed another thing while watching the videos—the bird’s beak snaps closed as soon as it is bent to the maximum.
"Their beaks snap shut in less than a hundredth of a second. It’s fast," he said. "They’re also incredibly thin. This makes their lower beaks stiff yet springy, like a diving board."
The ability arises from a bony hinge beneath the lower beak, which is composed of cartilage in most other bird species.
Yanega teamed up with two other scientists to explain the controlled elastic snap with a mathematical model. They found that the downward bend of the lower beak stores elastic energy in the hinge bone which triggers the rapid closure.
This snap-buckling action is seen in some plants and insects, but this is the first time it has been observed in a vertebrate.
"The classic example of snap-buckling in plants is the venus flytrap, which uses this trick to catch insects," said first author and engineer Matthew Smith in the release.
"Cicadas, too, have tiny ribs which they snap-buckle to produce their distinctive song."
