Migrating IS walking your dog. A structured walk.
Dogs are genetically programmed to migrate in search of food, shelter and territory. It is the term that most behaviorists use to describe "roaming in search of". It's just a word to describe the style of walking that a dog does when he or she is on a mission.
Numerous times, i've made people change their walking styles because their dogs can not handle having a territory. The dogs have severe anxiety.
Edited to add:
We, humans, tend to be guilty of applying human psychology to our canine companions. We assume our dogs enjoy leisurely walks where they get to stop every 3 feet and urinate. We often think "wow, how can one dog pee so much?". That is because your dogs stops and lifts it's leg or squats and lets a little urine out at a time but always seems to have some in reserve. The truth is, they are marking "their territory" and this gives them anxiety! Think about it, everyday you do this leisurely walk where your dog marks every spot that he or she can. The next day, you go on another leisurely walk and your dog starts sniffing the same spots and realizes that some other dog has come along and marked over the area that they claimed the day before. This happens every day, 7 days a week for a month to a year. Wouldn't you feel anxious over "who's been invading my territory?" That would be like someone entering your house every day and you couldn't stop them from sitting on your couch and watching. You have NO control over the situation. All you can do is repeatedly ask for that person to leave your house but, yet, they never do. Dogs do not see the world as us, they see it in terms of what is theirs and what is not.
Of course this is is also assuming we know what they are feeling when they mark, don't ya think?