Most people think of migration as the seasonal movement of a flock of birds between their breeding and non-breeding sites. In fact, bird migration is probably the biological phenomenon that has attracted the most interest among non-scientists, and has one of the longest traditions of scientific investigation in biology (Berthold 2001). However, there are many other forms of animal migration, including journeys between east and west, complex round-trips involving land and ocean, altitudinal journeys up and down mountains, and vertical movements through the water column of oceans and lakes (Hoare 2009). What sets migration apart from other forms of movements is that migration typically involves travelling from one type of habitat to another (Aidley 1981).