I've seen several tropical halls and free-flight aviaries that keep especially birds from several continents together - in some cases apparently to allow the public to see as many colorful birds as possible in the same place, sometimes as a temporary solution, and sometimes when a geo zoo doesn't have, say, an Asia department and hence has to keep an Asian bird in the African aviary.
Examples on top of my head...
Doesn't Burgers Bush have animals from all the world free-ranging? I've never been there.
Randers Regnskov in Denmark does this at times. At the start, their domes didn't have a continental theme, so the collection in each dome was quite a mix. Even nowadays, it happens - recently, they got a crowned pigeon that is now living in their South America dome (they don't have an Australia dome), and recently a quite lecherous male macaw moved into the Africa dome because it kept seducing female macaws of other species.
Copenhagen Zoo's and Guldborgsund Zoo's tropical halls also have animals from several continents.
Munkholm Zoo's free-flight aviary has birds from all continents except for Antarctica.
Quite a lot of rainforest exhibits have blue quails as natural pest control.