I will try to limit my reply to South America, not necessarily in order, but here goes 10 great destinations with suitable infra-structure (there are even better places, but with no structure for the travelling birder):
- Parque do Zizo private reserve: in the middle of the largest Atlantic Rainforest reminiscent, sitting in the middle of prime rainforest. Several rare birds sighted here, as well as many endemics.
- Itatiaia: specially the higher parts, where you can find the high altitude specialties that pretty much only occur there.
- Lagoa do Peixe N.P.: in south Brazil this big brackish water shallow lagoon is the winter destination of a huge number arctic and antartic shorebirds and terns as well as flamingos and a bunch of other cool birds.
- Pantanal: the biggest wetland in the world is home to a huge number of water birds, raptors, etc. Great wildlife watching too (as in mammals), no place on Earth is as easy to see a wild jaguar for instance.
- Falklands: never been there but the place is great for many saltwater birds, like albatrosses, penguins, shearwaters, etc. Several ducks inland too.
I'll think of other places soon...