Usually I "over crank" the camera - runs it at a twice normal frame rate, so that with a normal playback speed the overall effect is 2X slo-mo. This helps see more detail of the very fast hummer movements, as well as extending the duration of some of my very short film clips (often the birds only feed for a few seconds). I have finally discovered that audio recording is disenabled when overcranking, which accounts for the silent sound track in most of my movies (except in those cases I added a musical accompaniment). This is not stated in the (very long) camera handbook, but has been confirmed by a Canon technician. Initially I paid little attention to the sound track, in part because my hearing has still not recovered properly from snorkelling in the Bahamas.
The above fifth of july sequence was taken at normal framerate and clearly has a sound track! This spectacle went on for an hour.
The next Coral sequence shows the other extreme: it was overcranked (no sound track) and then slowed a further 8 times, so the total slo mo is 16 X! But one still cannot properly see the wing motion. I suspect this is because I'm not using a fast enough shutter speed (I'm using an automatic focus mode). I will experiment further. In principle with 16 X slo mo it should be possible to see the wing movements in detail (they beat at 50 times a second).