I'm still waiting for the arrival of the Mute Swan in the game, one of my favorite animals Graceful, majestic and so beautiful I don't understand that it hasn't been added yet
Mute swan and Mallard ducks would be the best introduction into birds personally, a wetlands area with swans and ducks is a common sight in zoos which major in bird collections. Red crowned cranes are our only realistic option for wetland areas right now , I don't count flamingos as such since they are mainly standalone habitats near African areas
I'd love to see some kind of swan, at least, though I vote for the trumpeter swan (they're just so huge). But mute swans are very pretty, and they are staples in most zoos with waterfowl ponds, so I'd use certainly use them in my zoos. Other types of waterfowl would be cool too. So many ducks and geese, so little time...
I personally would like Black swan more. Mainly cause in general European and north american animals just don't feel as cool and exotic as other ones. Same rule applies in why I want a mandarin or whistling duck over a basic Mallard.