Bird Wing Shape Reveals the Ancestry of Birds

The shape of a bird's wing depends largely on its ancestors. Scientists have found that the shape of bird wings is influenced more by how closely related species are to one another than by flight style.

Bird wings, unlike airplane wings, are flexible and change shape during flight. This means that their geometry and wing outline may not tell the whole story of a particular flight style or environment.

In this latest study, the researchers compared geometry across species and clades, which are groups of organisms that evolved from a common ancestor. In the end, the scientists found that birds that are closely related evolutionarily have similar wing structures, even if the birds show very different flight styles.

For example, albatrosses, penguins, and loons all belong to the clade Aequornithes and despite looking very different, all have a wing shape that's similar.

The findings also showed that wing shape became more varied as different clades diverged from early ancestors. There was an interesting exception to this trend, though, in the wings of Passerines, which include songbirds. Their wing shape resembled Galliformes, which is a distantly related order that includes birds whose direct ancestors were among the first birds on the planet.

"There's no existing hypothesis to explain that pattern," said Julia Clarke, one of the researchers, in a news release. "So a question now is why the length of these feathers tends to be similar and why they show similar trends across birds. We could be looking for a developmental explanation or a functional one."

The findings are published in the journal Proceedings of the Royal Society B: Biological Sciences.

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