Found it hard to catch these gals, they seem to dive frequently staying down for 45 secs(I timed 'em). I was lying on my side on the bank for this one.
I wish the light had been more uniform
1/640, ISO 800, Ev +0.67 f 8
40D 100-400 +1.4 TC
Rich
Getting low is a good choice Richard. Unfortunately, the light direction and strength is really working against you here. The strong side light has overexposed the left side of the bird and left the head in a mix of sun and shade.
The look over the shoulder can work as you get to see the head and the plumage on the back - try for more DOF to get more of the back in focus.
What would have been best here is frontal lighting as that would have lessen shadows and let you expose for the highlights. I have this problem all the time, I set up on the bank but the one I want never gets in the right light.
Nice looking duck but difficult conditions as Robert as commented on. Agree with your advice re removing TC as it would slow focus as well. Critical focus seems to be on the back and the head/eye looks a bit soft but ?is motion blur. Water drops are great.