We measured the variables of angle of diversion, vertical take-off angle, and sinuosity using stereo triangulation based on the position of the bird bills in two calibrated cameras. This process was completed in MATLAB (R2012a) using the Calibration Toolbox for MATLAB (http://www.vision.caltech.edu/bouguetj/calib_doc/index.html, Bouguet) and is detailed in Appendix 1. The output of this method is the three dimensional position of the bill in each frame of flight relative to a constant reference point. The start of flight was the three dimensional position of the bill of the animal in the frame before it spread its wings to fly. The small size of the enclosure seemed to encourage some animals to change direction sharply (>90°) once near a portion of the vegetative cover. We only used the flights before this change in direction, if present. If there was no sharp change in direction, we used the flight until the bird crossed the outside, bottom edge of the enclosure in the view of either overhead camera. We measured the angle of diversion from the path of the vehicle by comparing the direction of the flight to the direction of the vehicle approach (°). We measured the vertical take-off angle (°) when the animal passed 50 cm from the start of flight. A distance of 50 cm was chosen because it was within the range of distances used to measure take-off angle in other studies (Kullberg et al., 1998 and Lind et al., 2002). We measured the vertical take-off angle by measuring the angle (°) of the flight compared to a line at the level of the bird bill at the start of flight, parallel to the ground. Sinuosity is a measure of the directness of the flight, and was calculated by dividing the sum of the distances traveled by the distance from the start to the end of the flight (unitless, with 1 indicating a direct flight of a straight line and values > 1 indicating increasingly less direct flights). Descriptions of all the dependent variables can be found in Appendix 1.