Hummingbirds excel at maneuvering and flying through tight spaces

Flying animals (birds, bats and insects) often negotiate cluttered environments, sometimes involving the need to safely transit through tight spaces between obstacles. Considering their remarkable flight capabilities, hummingbirds are suitable for gaining a better understanding of how flying animals transit tight passages. We studied wild ruby-throated hummingbirds (Archilochus colubris) transiting a chain-link fence with openings smaller than their wingspan to reach a feeder. We identified two distinct flight strategies, involving swept-wing versus sideways styles. Swept-wing transits were characterized by interrupted flapping and a retracted posture with a ballistic body trajectory and were faster than sideways transits, which involved continuous flapping with a reduced wingbeat amplitude, higher wingbeat frequencies and more uniform body pitch and yaw compared with the body movements dynamics used in swept-wing transits. Our novel data for free-flying hummingbirds voluntarily negotiating narrow openings to access food reinforce earlier findings of captive hummingbirds, demonstrating that some fliers can modulate their wing kinematics and body rotations sufficiently to safely navigate openings smaller than their wingspan, a finding that may reflect a more general strategy across fliers. This study contributes both to understanding biological flight dynamics in cluttered environments and potentially to informing the design of autonomous aerial vehicles.