What kind of Nikon Lens are preferred for wildlife photography?

Answer 1

There is a whole raft of high-priced lenses in prime focal lengths. If you are asking this question here, you are not in that market. I have a couple of under-$1,000 suggestions for you.

When you say "nature photography," it makes me think of shooting pictures of animals with a telelphoto lens. If this is what you are talking about, I'd say the longer the lens – the better. I just got a Nikon 70-300 VR lens and I can tell that I will really get some use out of this for nature photography. I've just uploaded a couple of pictures to my Flickr site that I took with this lens. See if you think you can use 300 mm. (On the D40, this would be the "equivalent" of a 450 mm lens, exactly as it is on my D200.)

Nikon 70-300 mm VR lens:
300 mm (450 mm equivalent): http://www.flickr.com/photos/samfeinstein/536590467/
300 mm (450 mm equivalent): http://www.flickr.com/photos/samfeinstein/535497558/

Nikon 18-200 mm VR lens:
200 mm (300 mm equivalent): http://www.flickr.com/photos/samfeinstein/489450858/
200 mm (300 mm equivalent):
http://www.flickr.com/photos/samfeinstein/487852172/
200 mm (300 mm equivalent):
http://www.flickr.com/photos/samfeinstein/409564893/
200 mm (300 mm equivalent):
http://www.flickr.com/photos/samfeinstein/409564897/
200 mm (300 mm equivalent):
http://www.flickr.com/photos/samfeinstein/408446616/

Then again, maybe this is what you mean...
Nikon 60 mm f/2.8 macro lens:
http://www.flickr.com/photos/samfeinstein/487790706/

Answer 2

Probably 300mm to 400mm, preferably with Image Stabilization. Carrying a monopod would be a good idea.

Answer 3

f4 400m, or f5.6 600mm, a teleconverter may be usefull also

wildlife like lions etc??

a