Meeting Abstract
Previous studies have demonstrated that at medium and fast flight speeds, bird tails aid with maneuverability and drag reduction. However, little is known about tail function during slow flight in wild birds when display and locomotor demands may co-occur. Wild American Goldfinches (Spinus tristis) perform remarkable aerobatic maneuvers around bird feeders, particularly in the presence of conspecifics, and have striking black and white markings on their tail feathers. We hypothesized that goldfinches approaching the feeder use their tails for behavioral signaling, pitch maneuverability, and to increase drag, but the primary function varies based on the presence of other birds. For example, we predicted that finches approaching another finch would spread and depress their tails more than solo finches, even at very slow velocities when the tail has little aerodynamic effect. High speed cameras (250 frames per second) were used to record American Goldfinches during landing, takeoff, and slow flight around established feeders. We reconstructed the 3D kinematics of the body and tails using Argus, and calculated tail angle of attack, spread angle, and surface area. ANOVA analyses showed that tail angle of attack during takeoff was significantly lower than in landing or flight. However, the presence of other birds did not significantly affect either tail angle of attack or surface area. These results suggest that display is secondary to aerodynamic functions, even in slow flight.
