Seabirds have evolved numerous adaptations that allow them to thrive under hostile conditions. Many seabirds share similar colour patterns, often with dark wings, suggesting that their coloration might be adaptive. Interestingly, these darker wings become hotter when birds fly under high solar irradiance, and previous studies on aerofoils have provided evidence that aerofoil surface heating can affect the ratio between lift and drag, i.e. flight efficiency. However, whether this effect benefits birds remains unknown. Here, we first used phylogenetic analyses to show that strictly oceanic seabirds with a higher glide performance (optimized by reduced sink rates, i.e. the altitude lost over time) have evolved darker wings, potentially as an additional adaptation to improve flight. Using wind tunnel experiments, we then showed that radiative heating of bird wings indeed improves their flight efficiency. These results illustrate that seabirds may have evolved wing pigmentation in part through selection for flight performance under extreme ocean conditions. We suggest that other bird clades, particularly long-distance migrants, might also benefit from this effect and therefore might show similar evolutionary trajectories. These findings may also serve as a guide for bioinspired innovations in aerospace and aviation, especially in low-speed regimes.

海鸟已经进化出许多适应能力，使它们能够在恶劣的条件下茁壮成长。许多海鸟具有相似的颜色模式，通常带有深色翅膀，这表明它们的颜色可能是适应性的。有趣的是，当鸟类在高太阳辐照度下飞行时，这些颜色较深的机翼会变得更热，而先前对机翼的研究提供了证据，表明机翼表面加热会影响升力和阻力之间的比率，即飞行效率。然而，这种影响是否有益于鸟类仍然未知。在这里，我们首先使用系统发育分析来表明具有更高滑翔性能（通过降低下沉率，即随着时间的推移损失的高度进行优化）的严格海洋海鸟进化出更暗的翅膀，可能作为改善飞行的额外适应。使用风洞实验，然后我们证明了鸟翅膀的辐射加热确实提高了它们的飞行效率。这些结果表明，海鸟可能部分通过在极端海洋条件下选择飞行性能而进化出翅膀色素沉着。我们建议其他鸟类进化枝，特别是长途迁徙者，也可能从这种效应中受益，因此可能显示出类似的进化轨迹。这些发现也可以作为航空航天领域的仿生创新指南，尤其是在低速系统中。也可能从这种效应中受益，因此可能显示出类似的进化轨迹。这些发现也可以作为航空航天领域的仿生创新指南，尤其是在低速系统中。也可能从这种效应中受益，因此可能显示出类似的进化轨迹。这些发现也可以作为航空航天领域的仿生创新指南，尤其是在低速系统中。