Depends what you're looking for. Newquay has an excellent one for Asian Passerines, pigeons and. Galliforms. Lotherton has a big African walkthrough for birds ranging from Crowned Cranes to Glossy Starlings.
The three best in North America are probably the Scripps and Owens avaries at San Diego zoo, and the Wings of Asia aviary at Zoo Miami. There are a couple of others prominent ones, but I think in terms of sheer size and species diversity these are the top three in the country.
Jurong have probably the best in Asia,while KL claim to have the largest(i doubt that). The aviary in hong kong is good too, but not as great as jurong.
For asian zoos: This walkthrough in Khao Kheow photograph by @LaughingDove : Edward youde aviary in Hong Kong by @FunkyGibbon : KL Bird park by @FunkyGibbon : Jurong's aviaries by @Zooish :
Those are some monster aviaries. You said KL holds the largest in Asia, do you also know by any change what the biggest in the world currently is?
Thanks. Newquay UK? Thanks. I visited Jurong about a year after the large aviary was opened. At that time it was the worlds largest. Thanks. Thanks. Thanks. All very impressive. Hope to get to KL., and possibly return to Singapore as well. One day....
KL Birdpark's claim is highly suspect. I think it is widely believed that they have added together the total volume of all of their aviaries, most but not all of which are adjoining. In any case, the park is mostly a disappointment. I told @Giant Panda I would make this case some time ago. I guess the time has finally come. I think the Edward Youde Aviary in Hong Kong is the best large walkthrough aviary in the world, or at least in Eurasia. My argument is as follows: The architecture is great. There's nothing wrong with netting over a natural valley, but I'm a big fan of gigantic metal superstructures, as long as they are attractively executed. The EYA's is (although it also make use of the terrain). Furthermore, the inside of the aviary contains a fantastic wooden 'canopy' walkway which is both pleasing to the eye, and offers great vantage points to virtually the whole of the enclosed space. This includes the floor of the aviary where it rises up at the sides. The vegetation inside the aviary is wonderful. There are a number of large buttressed rainforest trees, as well as a lot of secondary growth. The key point here is that there actually aren't that many of the big trees, which really allows you to view the entire space. It's not particularly representative of actual rainforest, but you certainly see a lot more birds. Finally we come to the species line-up. I'm not going to type it out, but the aviary is incredibly well stocked with a variety of passerines, galliforms, parrots, pigeons and other things you might expect. I think there were 40 species signed in total. Over the course of the (almost?) two hours I spent there I think I saw more than 30 of them, and crucially didn't see any that weren't signed. Typically this is an area where large walkthroughs are pretty atrocious but here the EYA shines. The only real complaint is that there are probably too many Bali Mynas, which seemed to dominate the aviary somewhat and push a lot of the smaller birds around. The Edward Youde Aviary is pure class. It is brilliantly designed, executed and maintained. Frankly I can't think of any large aviary in Europe** that could come close*, and the only serious competition in Asia, to my mind, is Jurong's Waterfall Aviary. So let's compare the two. The WA is much bigger. This has the advantage of giving you a much more realistic rainforest experience. However, you are far less likely to be able to find and view the inhabitants, although you will of course see something. The EYA is large enough to feel cavernous, but small enough that you will eventually track down all three species of leafbird inside. Plus, in the EYA, you will actually know that there are three species of leafbird, because the signage is so good. Have fun with that at Jurong. The WA has an extensive path system, however it requires a lot of climbing and doubling back to cover all of it. At the Edward Youde you enter at the top and follow a gently sloping path to the bottom with the occasional short viewing cul-de-sac. You obviously have to pay Jurong's entrance fee to access the Waterfall Aviary; amazingly the EYA is located in Hong Kong Park and it and a few attached aviaries are free of charge. I might be hyping the Edward Youde a little bit, but I was blown away on my visit last year and I think it is tragically undermentioned on ZooChat. Hopefully I've redressed that a little bit tonight. *Giant rainforest houses are technically walkthrough aviaries and at least with regards to Masoala I would say it is a much better zoo exhibit; however the reasons it is better have very little to do with the birds it holds and so I don't really think it is under consideration here. ** Presumably the only ones in America would be the two/three at San Diego. Sadly I have no experience to draw on there.
Having been to San Diego and Miami, I far prefer the latter. I can’t find accurate size representations online for San Diego, but Wings of Asia at Miami was a brilliantly sized 1.24 acres that I could get lost while looking for birds in. It’s so lushly planted that it gives the birds a good chance to hide, but they are not impossible to see. Even the smallest and least numerous birds (just a pair each of hooded pitta and fawn-breasted bowerbird, as well as the lone Indian pygmy-goose) were seen multiple times by myself and I’m confident that had the weather not been so poor when I went I would have seen every species in it. This is no small accomplishment considering it houses about 500 birds of 85 species, which is practically double that of Owens Aviary, the most species-rich of San Diego’s big ones. My lone complaint is that the signage is rather severely outdated, often listed species no longer present. That said, volunteers within the aviary carry an up to date list so you will always know what’s present in there.
I would also add that Jurong's aviary, while still being a magnificent sight, is looking a bit rundown. The monorail (+ station inside the aviary) has been closed and there is very little theming regarding the bird species (lapwings, guinea fowl, weaver finch alongside rainforest spp). Many are seen elsewhere in the park. Not a patch on how it looked 20 years ago. I presume all of this is due to the imminent move of the park to a new location.
As the original question was for the best, which doesn't necessarily need to be the largest, aviaries, I'd like to add the aviaries at Bioparc de Doué-la-Fontaine, the main aviary at Tierpark Hellabrunn (Munich) and the bird of prey aviary at Zoo Schmiding to the already suggested examples.
