Most Bird Wings Aren’t Optimized for Flight
We like to think of natural selection as a ruthlessly efficient engineer, shaping organisms toward their ideal forms over millions of years of evolution. But the reality is much more complicated. Phylogenetic inertia, physical constraints, evolutionary trade-offs, etc. can lead to strange “design choices”. According to a new study published in Natural communicationsbird wings even seem to qualify.
To study the optimization of bird wings, researchers at the University of Bristol decided to design them from scratch. They created a “theoretical morphospace” of all the wing shapes that could appear in nature, whether they’re actually there or not (and they really covered their bases: some of the imagined wings were almost round while others were spindly wisps). They then tested each wing to find out which shapes worked best in different flight modes (soaring, hovering, diving, etc.).
After identifying the ideal theoretical wings, they mapped real bird wings to see how they measured up. Most birds don’t have the “best” wing shapes, they found. In fact, the majority of birds were in the middle to bottom of the optimization space. “It turns out that for many birds, including most of the ones you see every day, good enough is good enough when it comes to flight,” study author Benton Walters said in a statement.
Read more: “Why birds can fly over Mount Everest”
Oddly enough, hummingbirds and penguins had some of the most optimized wings (the flightless rhea’s least optimized wings weren’t such a surprise).
“Two groups of birds that surprised me because they were suboptimal were albatrosses and terns, both famous for their long-distance flight across the globe,” Walters said. “It turns out that you don’t need to be in tip-top shape to achieve the impressive feat of migrating from the Arctic to the Antarctic and back every year, as Arctic Terns do.”
But why aren’t wings generally better optimized for flight? After all, birds have been evolving for tens of millions of years, so shouldn’t their wings be a little better than mediocre in their primary means of locomotion?
Researchers have offered some explanations. First, it is possible that constraints acting on the shape of the wings involve their relationship to the rest of the bird’s body, which the study did not investigate. Additionally, many birds use their wings for other things, like courtship displays, and the wings most effective at attracting mates might be less optimized for flight.
Whatever the reason, the sleek, unoptimized bird wing is a beautiful reminder of the messiness of nature and that “good enough” design is often the best.
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Main image: Nick Dale / Adobe Stock
