Hello vimash, and welcome to the friendly Camera Labs forum!
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As to your question, I'm not sure what kind of suggestions you're looking for!? But kpr, a very active member of this forum in the wild-life and birding threads seems very fond of this lens. It's still on sale from Sigma but what I would sorely miss is the image stabilization.
An alternative would be the Sigma AF 150-500mm 5.0-6.3 DG APO HSM OS which has a built-in stabilizer.
Thomas (beware: Nikon-fanboy and moderator!) My Lens Reviews
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