Bat Migration and Hibernation is all based on the supply of food. Like every living creature on this planet bats need to eat to stay alive and this is the driving force behind their migratory habits.
There is a wide range of behavior among various bat species as to whether they hibernate or migrate or a combination of both. The general rule of thumb is that the bats migrate to available food sources.
Although sometimes bats that normally migrate may spend time in hibernation if they feel the expenditure of energy does not justify moving to a new location. It takes a lot of energy to fly long distances during migration, so there has to be big payoff at the end of the flight to restock calories lost during long flight times.
So their are species of bats that both hibernate and migrate depending on various factors such as food supply , inclement weather geographical location and migration distances.
Another interesting factor is that bats do not always travel from north to south or latitudinal directions. They may travel in any direction depending on the location of their hibernaculum.
Studies show that while birds migrate to exploit seasonal food resources, the majority of bats species migrate to find better hibernating conditions, although the vast majority of bat species hibernate as opposed to migration.