Hi Jon, very cool behavior you captured. I like the colors on the grebes and the clear view of their head/eyes... If you have more room id suggest a pano, also maybe some cw rotation. Well done.
Hi Jon, I like the behavioural aspect and the low POV, did the Angle finder come into play?
I agree with Ann that it requires a small CW rotation, however was the RH Grebe slightly behind, ie if viewed head on slightly to the right? I might have gone for f/5.6, 1/3200 as you had loads of ISO, but the 1D for frame rate here. I'm guess the FP was on the rear Grebe, tough conditions with all that water for it to lock on, I think you did well here.