The Secrets Behind Hummingbirds' Flight Agility Revealed: Which traits best allow hummingbirds to turn on a dime, in midair, at fast speeds? A new study reveals that the most agile hummingbirds owe their nimbleness to muscle capacity and wing morphology. Studies aiming to tease apart the best traits for agile flight have often been limited to single species, or involve constraints where animals to must complete a predefined task. To gain a more complete understanding of traits that contribute to flight agility, Roslyn Dakin and colleagues studied thousands of accelerations, rotations, and turns from more than 200 hummingbirds across 25 species. The birds flew randomly in an enclosed area, while a computer tracking system recorded their movements. Remarkably, the differences between species was distinct enough that the authors could correctly classify species in 34% of cases based solely on their maneuvering patterns, indicating that differences among species in maneuvering style are subtle but significant. Muscle capacity was associated with better deacceleration, accelerating on a dime, and upward rotations, the authors found. Wing loading, which is the ratio of the wing area compared to body mass, was associated with better rotational movement, and turns in general. Since muscle capacity was found to be the primary species-level trait associated with accelerations, the authors suggest that evolved changes in muscle capacity may be able to compensate for relatively small wing size. Peter C. Wainwright discusses these findings in a related Perspective.