I'd not worry too much about what continent one might be standing on. Just get a couple lenses that work. For wildlife something in the 100-400 range and indoors maybe 28-135 mm. Not met many that were happy with the extreme zooms like 18mm and out, as they're quite wanting in early and late light when stretched out.
Agreed. That is what I am noticing with the Tamron 18-270.
Duckster pictures are amazing, and seems like getting a 100-400 would be better use of money, as indoors and in controlled situations the Tamron with an aftermarket flash works great.
