Do you find you typically crop images from your D7000?
If the answer is yes, then I think you have nothing to gain from D800 and would be better served waiting for the D400. Once you crop the D800 image to or past DX lines, you've basically go the same resolution and same frame rate as the D7000, standing to gain (theoretically) in noise or dynamic range performance from the newer D800 tech. I think that's not $3000 worth of upgrade.
For bird shooting, I wholeheartedly agree with the previous poster that both cameras you're talking about have too limited a frame rate. With a D7000 in my bag, my D300s is still my go-to bird camera for its 7fps, and I expect it to remain so after I take delivery of D800. D800 will be a killer landscape camera, but it's a specialized machine. The low frame rate creates a liability for distant, fast-moving wildlife.