Congrats on your D700. It is one of the classic camera. Using a full frame after using a DX camera makes it look like you lack the "reach" that you are used to but I'm sure you'll enjoy the wider perspective in the long run.
I like the composition but agree with Marcel that it appears to be a little soft. I'm also wondering what it would look like if you hadn't cropped out the full reflection in the water. It might add to the composition of you include back the birds reflection....maybe.
Sorry for the delay, I shot with a Sigma 28-300 zoom, older model and I suspect now showing its lack of performance when plugged in to a D700, may have ot look for new glass ;( LOL