The growth of population depends upon the birth rate, death rate and migration. Movement of people from one area to the another area is called migration. Migration can be of a number of types.
According to the nature of movement, this can be divided into (i) permanent and (ii) temporary.
Permanent migration involves movement of people from one place to the other and these people do not go back to their original place. A common example of this type of migration is provided by the movement of the people from rural to urban areas for permanent settlement.
In case of temporary migration, the people move from one place to the other for some duration and then return to their original place of living. An example of this movement is seasonal migration. Migration of agricultural labourers from Bihar to Punjab and Haryana during the harvesting season is a temporary migration.
Migration can be on daily basis also. A large number of people commute to the cities every day in the morning from the surrounding areas to work and they all go back in the evening. This is called daily or diurnal migration.
It is seen in mountainous regions that many people move from valleys to the higher reaches of mountains along with their cattle during summer and come back to the valleys during the winter. These people have their permanent homes in the valleys and they move to the higher areas to graze their cattle there. When the higher reaches of the mountains become too cold, they come back to the lower valleys. Their annual movement is always along some fixed routes and generally their grazing areas are also fixed. This type of altitudinal migration is called trans-humance.
Gaddi tribes of Himachal Pradesh and Bakrawals in Jammu & Kashmir practises this type of migration. On the basis of source of origin and destination of migrant population, migration can be divided into four types: