Wild turkeys spend the day walking and scratching for acorns, seeds and insects, which is where the ground-bird impression comes from. At dusk the behaviour changes completely. Birds fly up into mature trees, often heavy-limbed oaks or pines, and roost there through the night, out of reach of most terrestrial predators.
The flight is powerful but short. Wild turkeys burst from the ground with rapid wingbeats and can cover a few hundred metres, with brief speeds commonly cited around 80 kilometres per hour. They do not sustain flight over long distances, and they travel between feeding areas on foot.
The confusion comes from the farmyard. Commercial broad-breasted domestic turkeys have been bred for breast mass to the point that flight is not possible, and that bird, not its wild ancestor, is the one most people have seen.