Many photographers invest in one of the big super-telephoto lenses in order to capture photographs of birds and other small animals. Although I use my Nikon 500VR lens to photograph birds on occasion, I tend to use it more for the following purposes:
My 500VR lens got a workout at the reenactment activities commemorating the 150th anniversary of the Civil War battles at Gettysburg. The lens enabled me to get a closer view of the action. It compressed the battlefield--helping to make the scene appear more congested. Finally, the narrow field of view helped to keep unwanted elements (e.g., spectators, cars, etc.) out of the frame.
Other events where the 500VR is beneficial include air shows.
The 500VR helps to simplify and compress landscape images. The narrow field of view also enables me to select just a small portion of the landscape to feature in the photograph.
The 500VR lens lets me fill the frame when photographing larger animals at the zoo. The extended reach of the lens means that little or no cropping of the frame is required during post processing, which yields higher image quality.
And, let's not forget the birds. It's a great lens for photographing birds.
Personally, I think it makes it easier to create more interesting photographs when shooting at the extremes of the focal length scale. I find myself shooting at either the 14mm (my widest lens) or the 500mm (my narrowest lens) focal length for a high percentage of my shots.