I realized I apparently had this object on a previous sequence of webcam shots captured in March, 2010. Those time lapse shots are 1 second apart, but the object was at the top of the frame and the "wing" was cut-off at the top. It took 8 seconds for this object to traverse the top of the frame from right left in that sequence. I may try to work those 8 frames up as a video clip one of these days.