As it should be no surprise to anyone, trying to take flight when you're as big as I am can be a bit of a bother. So on medium and short distances I tend to prefer to run along the ground when possible... And with as long strides as I take, I can build up quite a bit of speed over flat ground! It also helps that my tail and heads are excellent at keeping my balance at high speeds as well. Besides, you don't really learn your territory flying above it, and it's much easier to keep a presence in it when you're moving about on the ground!
Despite having wings, Rook spends a good bit of time on the ground. I'm really happy with how AltairXXX rendered Rook running along the ground here! I imagine that Rook moves quite a lot like a raptor, only quite a bit bigger, though not quite as agile.