I suggest you do some more research, starting here:

http://photozone.de/

That is a European website that does in-depth lens reviews.


I am not so sure that a mono-pod will be sufficient for such a large focal length.
The serious wildlife photographers use a very sturdy tripod.

When shooting from a tripod, it is usually advisable not to use "image stabilization", so that feature may not be too useful for you.

......

Here is a website by Sue Tranter.

http://www.suesbirdphotos.co.uk/

She specializes in birds and often gives details about lenses and cameras.
She has not been too active for the past few years, but her website is a treasure of wonderful examples.

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