My reasoning for this part was that they are all species that don't move much, and it doesn't feel wrong for them not to move. And yes, they do loop, but in very subtle ways, like heads slowy moving, unlike an active creature moving around in circles, which would seem much more repetitive. That's my logic. And I do agree that since we have flamingos and peafowl, flying birds that spend a majority of time foraging on the ground could be added, and not feel too out of place. Storks, pheasants, cranes (hopefully Afterican crowned, and perhaps sandhill, whooping cranes are nice, but I find sandhills more iconic to NA, mostly do to the rarity of whoopings. Or maybe all three), turkeys, ducks, the list goes on.