My first post here. A picture I took a few years ago, when I just bought my 400mm f/5.6. A bit too noisy, but I was going for BIF pictures and had my 40D at iso 800 . Taken at f7.1 and 1/3200sec.
I see Grey Herons once in a while but have not captured any half as well as you have -- very nice job!
I got lucky. The heron came flying straight at me but decided to take a different direction. It was just like he was going to stop in mid air. Took a very sharp turn to the left and disappeared.