I was photographing birds on the water when this flew right in front of me. I took a snapshot and was pleasantly surprised to see how well the focus locked on with the 1.4x extender mounted. The only frame I got and this is the full frame.
Canon 7D Mk2. Canon 100-400 L Mk2. Canon 1.4x Extender.
1/4000 @ f8 Auto ISO at 2000 + 1ev