Migration is the transfer or displacement of the population from one region to another or from one country to another, with the consequent change of residence; This movement constitutes a geographical phenomenon of relevant importance in the world.
Depending on the place of destination, migration can be internal, when it takes place within the same country; for example, from the countryside to the city (rural exodus); and external, when it occurs from one country to another. Both in the case of internal and external migrations we find the aspects of: immigration and emigration.
The immigration is represented by the population that enters a country or territory which is not born; supposes the entrance of population. And emigration is represented by the population that leaves one region or country and resides in another; represents population exit.
Migrants are called immigrants by the resident citizens of the country or region that welcomes them, and emigrants by the natives of the country that is abandoned; every migrant is an immigrant and an emigrant at the same time.
Two forces act on the migrant population: that of repulsion from the region of origin, caused by socioeconomic, political, religious, natural, family causes, etc.; and by attraction of the destination region, due to greater job opportunities, higher incomes, better services, generally better prospects.
In the past, migratory movements had different causes, from exodus made by large population groups for political reasons, religious persecution, wars and scarcity, to the colonization companies of the territories, discovered or conquered.
In current times, migrations are many and are mainly due to labor and political causes. Western Europe receives immigrants from Eastern Europe, Latin America and Africa; and the United States receives population from Latin America and Central America.
Just as there is human migration, there is also animal migration, the migration of animals can be temporary or temporary , if the species leave or are absent from their habitat and return again; or definitive when the species leave their territory and settle in others to reside there indefinitely.
In general, the causes of animal migration are the search for food or space to reproduce, change of climate, flee from predators, etc. Other important factors are environmental and sonic contamination by humans.
