My take is the relatively long exposure time the camera requires to capture an image using IR lighting and the speed of the object creates the impression of a long body because of the distance the object travels during a single exposure. (My camera offers exposure times from 1/15 to 1/450 but the IR only provides enough light for exposure settings in the 1/15 range.) Likewise the quad wings are the top and bottom of the object's rapid wing beat where there is a brief, very brief, pause as the beat changes direction. All of this together with what has appeared to be a forked tail in previous still images and the somewhat erratic flight path which is typical of the common nighthawk informs my guess as to its nature.
