Animals migrate from one place to another due to several reasons. They move from place to place so as to get proper living environment and food. Most seasonal migrants are birds, migrating south in the autumn and north the spring. In North America alone, more than five billion birds migrate back and forth each year. In a broad sense, migration is defined as the periodic passing of animals from one place to another.
In North America alone, more than five billion birds migrate back and forth each year. In a broad sense, migration is defined as the periodic passing of animals from one place to another. Migration is a two-way journey or a yearly round trip, with seasonal comings and goings. Thus, species of birds show periodic, to and from movement between their summer and winter homes or from a breeding and nesting place to a feeding and resting place.
Some birds may travel great distances between their two homes. During traveling they make the use of landmarks, such as coastlines, mountain ranges, rivers etc. as well as the positions of the sun, stars and the earth’s magnetic fields. These skills are typically programmed in their genes, but some birds learn routes from their parents. The birds show seasonal migration.
Kinds of Migration
- Latitudinal Migration: The migration of birds from north to south and vice-versa is called latitudinal migration. Birds are better-adapted to prolonged flight because of the gift of wings and conveniently explore two different parts of the earth. During winter season, the northern hemispheres are covered with ice and snow. The birds from this region migrate to south for food and shelters. Some birds of Siberia visit the wetlands of Terai in Nepal. Birds that feed in lakes (e.g. geese and ducks) or that eat insects (e.g. flycatchers and warblers) or nectar (humming birds) cannot find food during the cold winter months. The American Golden Plover migrates to Argentina and Africa to spend winter. They leave their frozen habitats and spend the winter in warmer places. In the spring, when more food is available in the north than the south, the birds return to their summer residences.
- Longitudinal Migration: The east to west and vice-versa migration of the birds is called longitudinal migration. Some birds perform longitudinal migration rather than latitudinal. For example, the starling moves from a breeding area in east Europe or Asia towards the Atlantic Coast to avoid the continental winter.
- Altitudinal Migration: The migration of the birds from high mountains to lowlands is called altitudinal or vertical migration. Some birds pass the summer in the mountainous regions, but return to the lowlands in winter. It occurs in violet green swallows of Great Britain and the willow ptarmigan of Siberia.
- Seasonal Migration: The movement of birds caused by season is called seasonal migration. In Britain, swifts, swallows, cuckoos and nightingales are summer visitors. They arrive from the south in spring for breeding and return to the south in autumn.. While the others like field-fare, snow bunting and redwing are winter visitors. They arrive from the north in autumn, enjoy the weather and return northwards in spring.
- Irregular or Vagrant Migration: A type of migration in which the birds may stray from their home and diperse in all directions is known as irregular or vagrant migration. For example, herons after breeding, the adults and young disperse in all directions over many or a few hundred miles in search of food and safety from the enemies. Some other birds like thrushes, warblers etc. fly at high altitudes in violent, powerful winds and sweep from west to east around the globe.