I'm not a huge bird fan, but the San Diego Zoo has an unbelievable collection in some of the most amazing aviaries on the planet. With the beautiful climate the birds have thrived at the zoo and the breeding record there is extremely impressive.
Owens Aviary has about 200 birds while the Scripps has around 130, and they are both two-level, spectacular achievements. Owens has birds from Southeast Asia and Australia, while Scripps has only African species. San Diego is a bird paradise, as there are still countless other exhibits scattered throughout the zoo grounds.
Yeah, at least before it's big renovation. Now it's laid out a lot more like Scripps. Treetop walkway and accompanying ground-level walkway, both from seperate entrances.
I liked both of these aviaries much more before they were renovated. In order to meet handicapped accessibility codes and handle ever-growing crowds, some of the original drama and intimacy was lost. Now the paths are so wide you really miss some of the feeling of being in the treetops (even though you are) or the feeling of being on a narrow jungle pathway next to a steep slope. And of course back in the day they stuffed these aviaries with many more birds than was probably appropriate, but wow what a collection.
They are still some of the most incredible zoo experiences on the planet, even more beautiful horticulturally than ever and probably doing better husbandry/breeding than in the past.
Trivia: the original Scripps aviary is seen briefly in "Citizen Kane" as a stand-in for the private zoo of the movie's protagonist.