Here's my list of recomended camera's in your price range:
DSLR
- Canon T3i - tons of used lenses available - 3x crop/zoom for video
- Nikon D3200 - tons of used lenses available - not as good in low light
Mirrorless
- Panasonic GH2 - awesome video and 2.7 crop/zoom for video - just ok for stills
- Sony NEX7 - incredible 24mpixel stills and video - limited lens availability
Point and Shoot - save the rest to take your wife on vacation
- Sony HX9V - awesome for everything except shallow depth of field
- Sony HV30V - a little bigger and more zoom
- Canon SX260 - incredible auto image quality
- - add a tines up scope)cam adaptor for incredible long range video and stills
The reason I put the point and shoots in there is that all interchangable lens cameras are a slippery slope. Results can be incredible, but the cost in dollars, weight and complexity go up exponentially relative to results.
As redrabbit said above, it's all in the lenses. The problem is that the latest and greatest lenses to really reach out and capture wildlife are unbelievably expensive. The newest Canon 600mm auto focus IS lens is $13,000 and weights 9 lbs !!!
Here's the best classifieds on the web for higher end camera equipment. Take a look around there for things that might catch your fancy.
http://www.fredmiranda.com/forum/board/10
Cheers,
Pete