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Animals are smart and adaptable, slowly evolving over the years to develop a method to cope during their most difficult times of the year. Typically called the annual migration, it ensures the survival of the species regardless what animal type it is. Migration itself is referred to as a large-scale seasonal movement of an animal population—complete or partial groups—from one area to another. A migrating animal often will return to breed where they were born or hatched, regardless of thousands of miles needed to get there.  This makes migration a major part of the animal's life cycle, as compared to "emigration" or removal migration where the animal's change to another location is not followed by a return journey.

MIGRATION FACTS

What makes animal migration fascinating is the ability of the animals to move geographically from one specific point to another. For example, migration of the barn swallow consists of returning home after an 1,800-mile round-trip, with the swallows traveling in a migratory single-line up to 600-miles in one day. The first swallows of San Juan Capistrano Mission had arrived in 1776 for their very first migratory path, considered the first migrants traveling every year in the fall. 

Difficult as it sounds, during migratory travel the swallow parent and their babies remain near each other throughout the long trip. Without getting lost, the animals use mental maps to navigate while seeking familiar landmarks--rivers, mountains, and coastlines—while using random and search-orientated methods. In conjunction, ecological and climate systems are used for clues to keep their bearing.

Migration patterns are typically connected to seasonal weather changes, mating, breeding, and feeding patterns. Exceptions to these are something referred to as "irruptive migrations", where these typical patterns are not followed. Instead, the act of migration is practiced by nomadic species who travel only when the food supplies are exhausted. These particular species consist of grazing animals such as the beautiful caribou or deer. In comparison are the Dall sheep of the Noatak National Preserve, known to move for seasonal and altitudinal migrations. They spend the summers at the tip of the mountain ranges, but during the winter remain at the lower elevations—all because of less snow and easier food sources.

SIGNS OF AN UPCOMING MIGRATION

Depending on the type of migration, typically a change in weather will start the animals moving. This is similar to the smell of fall we get toward summer's end, a sense that fall is soon approaching. These simple signs consist of shorter days and cooler temperatures, spurring animals toward preparing for their upcoming annual migration.

Exceptions involve animals that live close to the Equator. One explanation for the migration of these animals is that they become restless after too many days of no change, recognizing instinctively that it is time to begin their migration even though the weather has remained the same and the length of the days remain unchanged.

Most of the seasonal migrations involve the availability of food. When food becomes scarce or water ponds dry up, the animals simply move to survive.  But if overcrowding develops and food becomes scarce, another type of migration occurs to provide for the survival of the herd, with newer areas rich in grazing with less numbers. Signs of migration are not always so obvious, with genetics playing a big role in it. Science is now finding evidence that "animals inherit migratory routes from their parents genetically."