It's because there are more geese on that side.
Cuz Winterfell and it can't get up! :P
Why, wouldn't the winter be over by the time they reach, if they walk all the way along? So they fly.
They're not infallible
It's because that side has more geese.
Because there are more birds on that side.
Well, there's a reason for that. There are more geese on that side.