Please do tell that Photo 1 was taken by your girlfriend, too, like you're admitting to in your Flickr account. So it is not only the lens, but also her presence of mind to "be there" and take that pic while the tiger jumped!!! Honour to whom honour is due!
first off well done to your GF with the first shot!!!
Of the rest I have to say I like the 3rd from last (the bird) even though the bars are being a bit of a pain the background, the bird itself is well captured.
If you look there are little bits of animal cut off in several shots - its something that is very easily done when shooting (especailly wildlife which moves!!) - just remember to keep your eye on the boarders as well.
Also try renting out a 1.4Teleconverter as well as a 70-200mm f2.8 - the added range works well in a zoo (if you get another chance)
I agree and thats why I put it 1st.they are all awesome
but the first is the best!!