I love the fall reflection colors...the subtle ripples and reflection on the water is nice...but...as you already know...its to bad you could not get closer to the Grebe...but we take what we can get sometimes. ;)
The water is spectacular but I wish the bird were sharper. I'm not familiar with your camera and lens, so maybe some of the others here can comment on technique -- I wonder if the focus was right on the bird? It would take accurate spot focus with such a small subject, and it would be necessary to follow any movement in terms of distance changes to the subject -- but with a more distant subject the DOF isn't as critical as one very close. But it almost looks as if the DOF centers behind the bird.
But with such a large crop, your focus may be closer to expected tolerances. It is too frustrating not to have enough reach, or a too-distant subject. It's worth the extra time in the field to get a better opportunity than to try to salvage a distant shot afterwards.
Its been a bit of a battle against the light with the weather we have had here recently and it was just good to get some photos. This of course means your right and I was trying to salvage an image. I did get some shots of other subjects but without the autumn colours I was looking for.
Do you think the image would have worked if the focus on the grebe was better or do you think it would be too small in the frame anyway?
I think a very sharp bird would make this a good environmental image, but to get that kind of IQ on the bird, the shot as presented here couldn't be a crop. Getting enough pixels on the subject is critical to IQ. I always zoom in to 1:1 (100%) to evaluate a subject. There is less texture and detail in the water so cropping doesn't affect it as much, as long as noise is low.
A small-in-the-frame environmental image is strengthened by some framing from FG details, trees on one side, some OOF BG elements, etc. Items to look for when you can't get close to a subject. (And almost as hard to find as the subject itself.)