We measured the following behaviors: alert distance (AD), flight initiation distance (FID), angle of diversion, vertical take-off angle, and sinuosity. We recorded all behaviors separately for each of the two birds in the experimental enclosure for each approach. We measured the time of the first frame when the animal displayed alert and flight behaviors. An alert behavior was defined as a change in behavior or the rate of a behavior from the baseline, such as moving from a head down to a head up position, stretching the neck up, crouching, and freezing. A flight was defined as a walk or run away from the approaching vehicle, or a flight recorded the moment the animal began pushing off the ground. While we attempted to maintain a constant vehicle speed for all approaches, there was some measurable variation in vehicle speed that we included in our calculations. We calculated the vehicle speed by taking the distance between the cameras filming the vehicle approach and dividing it by the time it took the vehicle to travel that distance. We determined the time at which the vehicle would have collided with the enclosure, and measured the difference between that time and the time the animal displayed an alert or flight behavior. To measure the AD and FID, we multiplied that time by the speed of the vehicle.