Don Kuykendall_RIP
RIP :(
Jeff, if I was you, I'd stick around with both formats. Seeing you do birds with the Tamzooka, you would loose too much if you went FX exclusively. If you want to upgrade, then the 7100 would be an IQ improvement over the 7000, just how much I don't know though since I've never used the 7100. Pixel count seems to lead us to more, but in real life, a good shot is a good shot, even with a bit of noise. I'd rather spend my money on travel to get these shots than on newer (read more pixels) that I'd stare at in my living room.
Opinions will vary from others and that's quite normal too. In the end, you'll be deciding.
Good luck and don't rush it, you're shots are fine as they are and they sell... Would you sell more with a new body? I sincerely doubt it.
I think the combination of removing the optical low-pass filter (OLPF) plus the Extra horsepower in the MP really do make a big difference. My wife shoots the D7000 and I shoot the D7100 and we shoot together a lot so I see the same shot from both cameras all the time.