Migration is a behavior that is usually influenced by

a. changing seasons.

b. the phase of the moon.

c. the rise and fall of tides.

d. the time of day.

Let's take as an example the behavior of some birds, for example Storks. They live in Northern Europe in the Summer but travel South during the winter. This behaviour is actually called a seasonal migration and is dependent on the change of seasons - so the correct answer is a)