Originally posted by Rory Oh, and I do realize they'll work on the DX frame. The reasons I was thinking FF was:
A. Why not? Going to a company that offers it, why not go for it. Compared to a D300, I could find one used for $400/500 more.
B. The 70-200 would be much more useful to me on a FF than a crop. 105-300mm would be quite limited use, and would put me in the same boat as the 400mm (which would now be 600mm).
It all depends on your perspective (pun intended)
in many cases, while nikon offers full frame, for the longer tele's a cropped sensor is actually preferred, except in really low light.
If you consider the cropped sensor pixel count, and consider many times, unless you are really patient, you end up cropping down on the bird you photograph. As a result, you crop down less with the ASP-C sensor, and actually have more useable pixels than with full frame.
People go full frame for noise control, and for ultra wide angle, or simply because they can either afford to spend more, or believe it is a status thing. "i have a pro camera, I'm important"
as to your comment on birding, maybe you should open you eyes a little. See the attached link. To me the list looks pretty long
http://en.wikipedia.org/wiki/List_of_birds_of_Illinois