Fig. 4: Constancy of line-of-sight angle during the terminal attack trajectories of Swainson’s Hawks attacking Mexican Free-tailed Bats.
From: Raptors avoid the confusion effect by targeting fixed points in dense aerial prey aggregations
A, B Polar plots displaying the azimuth and elevation of the line-of-sight (LOS) from the hawk to the bat that it attempted to catch for all n = 62 attacks; the radial coordinate represents the bat’s range. The plotted lines are nearly radial, indicating that the attacked bat remains on a nearly constant bearing to the hawk. C, D Polar plots displaying LOS azimuth and elevation for 20 neighbouring bats tracked concurrently on each of four colour-coded attacks; darker lines display the LOS azimuth and elevation of the bat that was attacked. These darker lines are more nearly radial than the lighter lines displaying the LOS azimuth and elevation of the neighbouring bats, confirming that the constant-bearing geometry is specific to the attacked bat. Only one of these four flights (purple) ended in a successful capture: this attack displays the most nearly radial of the dark lines; this being the flight on which the collision conditions are most closely met.
