Outdoors, bird photography?

Perhaps a full frame camera is not the right camera, a crop sensor will give you a boost in your zoom range. Allowing you to capture birds that are farther away.

Going with the D600 or even a used D700 will give you extra money to spend on lenses.

Worry less about the body and more about the lens! Save $2000+ on a D7000 get a decent telephoto lens (like this one: http://lenshero.com/lens/Sigma-50-500mm-f4.5-6.3-DG-OS-HSM-APO-Nikon-f-lens )

If you look at the D800 vs D600 VS D7000. the comments about going with a D7000 to get the CROP (DX) is not valid. Both the D600 and D800 both can do either FX or DX.

www.exlusivephotoworks.com

I recommend the D7000 because of its high FPS rate (6+ FPS) and its smaller DX sized sensor will give an apparent increase in field of view while using a long telephoto lens. This means that you could use a 300mm f4 lens and get the FOV of a 450mm lens. This will be useful for shooting smaller birds or bids at a distance. I have used this lens for action sports and it works extremely well. Currently, this camera is the best Nikon has in the price/performance area for crop sensor sports cameras. The one disadvantage of FX is that you will get real focal lengths, so you will need a longer, faster, and more expensive lens to get the same range as a DX camera. That or you would have to use a teleconverter, which will reduce optical quality and light transmission of your lenses.

Forget Crop sensor, with Nikon D800 you could get a creative options to crop it & enhance composition. I have experienced it myself as I bought D800E recently.

use crop sensor cam like d7000 or tele convertor on d600 for extra reach

 I would go with D600 or D4 if you have money . I got D800, but cant recomend it due to WB problems and noise. D 600 is less noisy and cheaper !

I've been doing wildlife photography for the last 5 years and i would choose a crop sensor body any day! 

A DSLR with crop sensor is much better at capturing subjects far away, given their innate ability of default 1.5 zoom. Furthermore, you can spend the rest of your money on top quality lenses instead of buying a full-frame body.

It's lighter and more nimble for moving around. Also the lower pixel count on a same sized full frame sensor implies better lower light sensitivity. That has to be a good thing for compensating the relatively lower aperture value on the long focal length, contributes to a faster shutter speed for catching the moment. Apart from the technical advantages for shooting fast-moving objects, being lighter, D600 also is by large cheaper than the D800. 24.2 MP shall also just suffice the bird-shooting purpose much more than fine!

24mp the files are smaller but still more than enough quality.. so i would go for d600

- faster fps

- lighter

- cheaper

but Brenden-Sherratt says right, it isn't sure that you need to FF body.

Crop Sensor. Love this camera.

 This camera has everything, a great AF-system, Massive 12frames per second, a huge buffer, but the price is enormous too...so if you're looking for a cheaper alternative, I'd go with the 7d , or wait some time, there are some rumors that canon and nikon will release new cameras in january (probably 7d Mark II)