I see this most mornings out the kitchen sink window.  Hummers flocking around the nectar feeders, backlit with early morning sun.  I set the shutter speed to max  and ran the aperture setting up and down the stops, looking at the results on the LCD screen.  I wanted the bright glow in the nectar to dominate and to stop the motion so that the wings were sharp.  I forgot to change the ISO setting from auto so the camera ran it to the maximum of 3200, giving the photo that grainy look.