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I don't have the mentioned lense, but it's said to be rather slow, which I wouldn't recommend for birds. Depending on the size of animals and the distance 400mm can be pretty short. I tried to take full frame pictures from little bird in the garden with my 80-400 Tokina. I was only about 3.5m away from them!
A good recommendation would probably be a fast 400 or 500mm Lens (2.8 or 4) but that is horendously expensive.
Maybe someone else can give you good advice on that.
While bird photography does generally require long lenses, it also requires skill and planning. I got some excellent tight shots with my 70-300mm VR, of young fledgling birds on my balcony rail over the past couple of days, shooting out my window. Professional nature shooters set up blinds - like tents to hide in - where birds are likely to be found. They may also bait the area with bird-seed to entice the birds to the spot. This takes time and planning. The blind may have to be in place for weeks for the wildlife to come to accept it and ignore it. Even with the longest and most expensive lens in Nikon's arsenal, getting close is the most important factor.
I chose my 70-300mm over the 80-400mm for a number of reasons. Tests show that is is considerably sharper, it only weighs and costs only a third as much. Thus I am much more likely to carry it when I walk out to take photographs. On my D300 it is equivalent to a 105-450mm lens and on the D700 I have such high quality that I can afford to crop drastically if I need to. The D300 produces excellent quality at ISO1600 and the D700 is even better at ISO6400, so I don't need huge, expensive f/2.8 lenses. The lighter the lens, the more likely I am to bring it along.
When one gets up toward the super-telephoto range, it takes a lot of millimeters to make a significant difference in the angle of coverage. A 300mm covers 8Â° 15', a 400mm covers 6Â° 10' and a 600mm - 4Â° 10'. A great deal of weight and cost to only gain 2Â°.
In general, the more focal length you have, the more difficult it is to focus, and even at fairly small apertures, depth of field is very shallow. Any camera movement is also amplified as the length increases, and though VR is wonderful, it too has its limits.
a while ago I was looking for a good lense with a focal length of around 300-400mm (on a crop camera, D80).
First idea: Sigma 150-500. After some god advice of forums participants I decided to buy a secondhand 300/4. Just about a week ago a bought a TC14 EII. Now I have an excellent 300mm lense (quality is comparable to the 300/2.8, just not that fast and no VR) and a very good 420mm lense with my converter. The AF is fast, even with the converter and the pictures are just stunning.
One of my favourites!
So, if 300mm (or 420mm) are enough, you get a really good combination.