Perhaps the best mirrorless system for shooting wildlife, especially birds, is Nikon 1. The V3 is very fast and seems like the absolute best at tracking (among all mirrorless system cameras; haven't taken much time to research this camera, so definitely read the review here on DPReview). The native 70-300mm f/4.5-5.6, while expensive for a small-aperture zoom lens (at close to $1,000), gives great optical quality at an incredibly narrow field of view (equivalent to 189-810mm on a 35mm format sensor / film), and in a small, lightweight package.
Photography Life has the most comprehensive coverage of the Nikon 1 system of any website I've seen that also covers other formats. That coverage includes
a full written review of the aforementioned 70-300mm lens and, of course, the Nikon 1 cameras. The latest and greatest Nikon has to offer in that system is the V3. Another interesting article there is
Capturing birds in flight with a Nikon 1 V2 and FT-1 adapter, displaying photographs taken with the V2 and Nikon F-mount telephoto lenses adapted using Nikon's own adapter (which retains AF, AE, VR and all other electronic-dependent functions and features), and the photographer's thoughts on that combination.
That's pretty much it for wildlife in daylight. There are still two areas to cover: wildlife in dimmer light, and landscape photography.
That 70-300mm lens, combined with the Nikon 1 cameras' relatively small sensor, doesn't show much promise in low light conditions. The sensor's SNR (signal-to-noise ratio) at higher ISOs isn't particularly awful, though. I regularly use my E-M5 (Four Thirds sensor) at ISO 1600 and rarely hesitate to go to 3200, and I imagine I would have somewhat similar experiences with a 1"-type sensor in a V3. DxOMark shows the Four Thirds sensor has slightly less than a full stop advantage - roughly 2/3.
You can certainly mount "fast" Nikon F-mount lenses, like a 70-200mm f/2.8, 200m f/2 or 300mm f/2.8, but then the package won't be nearly as lightweight - you may as well get a DSLR that's made to be used with these lenses, which means it can probably focus them faster - that's theoretically speaking, I'm not really sure how it goes in practice.
In general, there's just no possible way to engineer a small, "fast" super telephoto lens. A system or fixed-lens camera that has one probably uses a small sensor (smaller than CX format), more or less negating its viability for freezing action in low light due to poor performance at high ISO. The Panasonic Lumix DMC-FZ200 seems like a good example here (being a 600mm equivalent, f/2.8 lens at the long end of its zoom range, with a tiny 1/2.33"-type image sensor as found in many compact cameras), though I've heard some photographers got decent results out of it in low light.
As for landscape photography, the V3 is definitely an unorthodox option. Lens choice isn't necessarily the problem - there is an ultra-wide zoom (6.7-13mm f/3.5-5.6), several zoom lenses that start at 10 or 11mm (moderate wide angle for the Nikon 1 system) and a 10mm f/2.8 prime. I'm not sure these lenses really perform well, though.
The main issue that makes cameras like the Nikon 1 V3 quite frustrating to use for landscape photography is the relatively narrow dynamic range at base ISO, limiting the flexibility of a single Raw file and often forcing the use of graduated filters or blending multiple exposures in the processing stage, to balance the tones of different elements in the scene and avoid blowing highlights (usually those blown highlights are the sky). This limitation can usually be worked around.
If you find the V3 (or any other Nikon 1 camera) isn't what you're looking for, then I suggest that you take a look at the Olympus OM-D E-M1, but ultimately go for a DSLR. They are simply better suited, as of now (it can definitely change when the next generation of mirrorless system cameras arrives), to shooting wildlife, especially birds in flight.
