I know that the devs have done very few birds due to reasons of flight issues, but I think there could be an easy solution. Many irl zoos have habitats that basically just have nets on the tops to prevent "escaping" which could easily be added. There are mesh wall pieces in decor, and I feel like they could be added into barriers as essentially just a cover for the top of the enclosure. There could be a way to just outline the barrier and select the mesh topper to make it habitable for flighted bird species.
On top of this idea, there could be different barrier types for the toppers, such as some sort of sizes of the mesh pattern and even the thickness of the wires that provide extra strength. On top of that, there could always be more flightless birds added as habitat species.
Another idea would be a new edition of the walkthrough exhibit, bigger and both optional for a walkthrough or not based on the species size. The walls could be mesh rather than the glass on the other basic exhibits. This could add the ability to have smaller bird species in the zoos without fear of escaping or lack of proper space for that species. While there would always be the idea that an animal could do with more space, these are just ideas to help increase the ability to add other birds to the game.
On top of this idea, there could be different barrier types for the toppers, such as some sort of sizes of the mesh pattern and even the thickness of the wires that provide extra strength. On top of that, there could always be more flightless birds added as habitat species.
Another idea would be a new edition of the walkthrough exhibit, bigger and both optional for a walkthrough or not based on the species size. The walls could be mesh rather than the glass on the other basic exhibits. This could add the ability to have smaller bird species in the zoos without fear of escaping or lack of proper space for that species. While there would always be the idea that an animal could do with more space, these are just ideas to help increase the ability to add other birds to the game.