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 other weird land behaviour, I don’t know if we’d still call them birds. Probably something like dino-saur, idk.