Blue Heron with 7Dmk2 and Sigma150-600 C

I was able to get these two pics over the weekend. I found the Sigma 150-600C at 600mm to be very difficult to handle and lock on focus with the 7Dmk2 in AI servo and central zone focus. These were to only acceptable images I got with that combination. I think the 100-400ISmk2 would have performed better but the reach was limited and this bird was spooked easily

Not an expert here but perhaps brighter sunlit foliage in bg was causing a problem?

Beautiful looking shots.