So, what is migration?
Migration is a natural phenomenon by which individuals of given species move between areas which they inhabit at different times of the year. Migratory movements tend to be regular and largely predictable. They may take place over large fronts or along thin, traditional routes; in one single, continuous journey or as a series of legs interspersed with rests. In this latter case, many species use regular staging areas as stop-over sites where they recover from the previous leg and gather fuel before they continue their trip.
