I have spent my evening thinking about other groups of birds that would definitely work in the walkthrough exhibit and could all be fairly easily made from a single model, and have settled on a collection of small birds comprising finches, buntings and tanagers. I have chosen one each for the six continents with such birds:
From North and Central America and the Caribbean is the
painted bunting. It is not that common in captivity, but still has a presence in zoos (six here in Europe) and is kept in walkthrough displays. Their in-game biomes would probably be grassland, temperate and tropical.
From South America is the
saffron finch, actually a very finch-like species of tanager. Slightly more common in captivity than the bunting, they have bright yellow plumage that makes them appear to be canary-like. Although often kept in rainforest displays in zoos, it is a bird of the grassland biome outside the Amazon Basin.
The third species is the
European greenfinch, which occurs throughout Europe, parts of west and central Asia and in north Africa. Surprisingly common in captivity, Zootierliste records it being kept in 40 European and 3 Israeli zoos. Biomes would be both grassland and temperate.
Occurring in a band extending across Africa, from west to east, just south of the Sahara, is the
red-cheeked cordon-bleu. It is not common in captivity, but is widespread in zoos. They would add a unique blue-and-pink plumage unusual among birds. The biome would almost certainly solely be grassland.
From Southeast Asia comes the
Java sparrow. While not the prettiest species on my list, with its mostly grey plumage, they are an Endangered bird and are also very common in captivity - Zootierliste records 160 zoos with the species in Europe, New Caledonia, Israel, New Zealand and Singapore. Biomes would be grassland and tropical.
Finally, from northern Australia is one of the most recognisable and best-known of the finches, the
gouldian finch. They are commonly-kept cagebirds, and Zootierliste records 107 places keeping them, in Europe, Israel, New Zealand and the UAE. I think the only in-game biome it would inhabit is grassland. It would be a bonus if they came with all three wild-type head colour variants (yellow, red and black, as seen below); if only one were possible I would probably choose the red-headed variant.
And with that, you'd have six beautiful birds that could all fit in to almost any part of a zoo and add a lot of colour and sound in the process.