Like, I’m aware of there being exceptions like Penguins, Ostriches, and Bats. But in general, why is there such a distinct land/air split between mammals and birds? Why don’t mammals share the ground with ecosystems of plant- and meat-eating walking birds? Why didn’t we get birds that evolved to slither like snakes, or tunnel like rodents? Why isn’t it (land+sky) all just mammals, where we’d have parrot- and vulture-like bats that don’t lay eggs? If we started the simulation again, might things like this evolve?
Peacocks and hens, Grouse and Turkeys, and some Phaesants spend most of their time on the ground. Ducks and Swans spend a lot of their time floating on water surfaces. Geese do fly and flock but are often in groups nipping at the ground, rather than in trees.
If birds slithered, tunneled or did other weird land behaviour, I don’t know if we’d still call them birds. Probably something like dino-saur, idk.