Well, if you are talking about people migrating rather than animals and birds, movement of people can be beneficial in certain select situations. People usually migrate or (move) because they expect to improve there lot in life. But to move inter provincial would probably relate to specific economic changes taking place in Canada. Of course it could be for bad reasons also, like living where you are is getting and expected to get worse. Hence to move from a declining situation to a declining situation which is declining slower may seem like an improvement in circumstance. Your question is so general though that any specific reasons will not develop.