From teeny hummingbirds to giant whooping cranes, roughly half of the world’s more than 10,000 bird species migrate. Longer wings and beefed-up flying muscles often help these birds crisscross vast expanses of air. But a study of nearly all bird species suggests many migrators share another unexpected flight aid: lighter-colored feathers.It’s known that color can help birds hide from predators by blending in, or attract mates by standing out. But color has subtler effects too, including regulating temperature by absorbing or reflecting light, says Kaspar Delhey, an ornithologist at the Max Planck Institute for Ornithology in Seewiesen, Germany. The longest-distance migrators were about 4 percent lighter than non-migrators, an effect that wasn’t explained by size, climate or habitat type for different species.
“It’s not a big difference,” Delhey says, noting that many migrators are darkly colored, perhaps for reasons unrelated to flight. But the trend was remarkably consistent.
“Very different groups with very different biologies show this pattern,” Delhey says. “That surprised us.”
“It’s not a big difference,” Delhey says, noting that many migrators are darkly colored, perhaps for reasons unrelated to flight. But the trend was remarkably consistent.
“Very different groups with very different biologies show this pattern,” Delhey says. “That surprised us.”
