Meeting Abstract

20.4  Friday, Jan. 4  High speed pursuit in barn and cliff swallows SHELTON, RM*; JACKSON, BE; HEDRICK, TL; Univ. of North Carolina, Chapel Hill; Univ. of North Carolina, Chapel Hill; Univ. of North Carolina, Chapel Hill rmshelto@email.unc.edu

Birds require visually guided interception techniques to catch prey in flight, to track down potential mates, and to chase off competitors. While the visually guided tracking strategies of various insects including houseflies, hoverflies, and dragonflies have been well documented through lab experiments, birds only exhibit these behaviors in natural settings. Here we used a set of three high-speed cameras to capture a series of barn and cliff swallow chase sequences where one bird follows the other through a series of turns, sprints, dives and climbs. From these recordings we extracted 3D body and wing kinematics including the instantaneous velocity, acceleration, angular velocity, and angular acceleration of each bird, and various distances and angles between the two birds. We found a strong correlation between the total accelerations, angular accelerations, and angular velocities of the two birds with phase lags of approximately 89 ms, 71 ms, and 87 ms, respectively. These phase lags are slightly larger than the mean wingbeat period of the chasing bird (~70ms) suggesting that these birds may only be able to initiate a major flight maneuver once per flapping cycle, and that the response latency of the trailing bird is the sum of neurosensory and biomechanical lags. No simple visual targeting model precisely fits the response of the trailing bird suggesting that swallows may use a combination of sensory cues in planning pursuits. When comparing the flapping latency between the lead and chasing birds we observed a non-random distribution which could contribute to a complex chasing algorithm.