Migration

Migration is a natural phenomenon that is observed across a broad range of animals and birds, from the tiniest butterflies to the massive blue whale. Therefore, every year, tons of animals set out on a journey that more or less spans the earth – this may be in search of shelter, water, food or a change in the climate. 

Moreover, these migratory animals often cover hundreds of thousands of miles in distance, by air, land or sea, pushing to the very limits of their strength and capacity. What is it that makes migration such a fascinating spectacle to look at? 

The definition of migration in science is stated as the movement of animals across long-distances, in search of food, better climate, or to find mates. This usually occurs on a seasonal basis, but can be annual as well.

Let us further look at what is migration in science and the various causes and factors behind it.

Factors Affecting Migration

As we mentioned above, most animals and birds migrate in search of food, shelter, warmer climes or a suitable mate. For instance, the Atlantic Salmon spends most of its lifetime in rivers, but occasionally migrates further downstream towards the ocean. Consequently, after having spent several years in the ocean, it returns to the river to lay its eggs. Thereupon, it begins its lifecycle all over again.

Many Possible Factors Govern Migration. These could be:

1. Natural disasters.

2. Climate change.

3. Droughts.

4. Shortage of food.

5. Shelter.

Vernal migrations, particularly, can be seen in many animals, most of them being birds. From the swallow to the turnstone, the osprey and the turtle dove, migration seems to be a typical pattern in all of them, especially during the winters.

Besides, more than 4000 species of birds migrate every year. This accounts for more than 40 per cent of the world’s total bird population.

Factors Affecting Bird Migration usually Includes:

1. An evolutionary response to seasonal variations. For example, the bar-tailed godwit covers the longest flight known among birds. It covers a whopping 7000 miles, leaving New Zealand and finally reaching the coasts of Korea or China. They do so in search of warm summer grounds to breed on.

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2. Furthermore, many migratory birds travel long distances in search of favourable water and food sources. To enumerate this, the turnstone flies to the wild forests of Greenland and Canada every year looking for fish, and a nice place to breed.

Pop Quiz 1

1. What do you Mean by Migration?

1. Long distances travelled by birds and animals.

2. The long distances birds and animals cover in search of food, shelter and better climate.

3. Immigration.

4. Hibernation.

Various Types of Migration 

Many birds, to prepare for the extreme feat of migration, enter a state called hyperphagia. In this, they fatten their bodies with extra amounts of food, so to last the long distances. This food helps provide additional energy when they need it on their long journeys.

Some birds even go to the extent of doubling their body mass. For instance, the blackpoll warbler, that drastically increases its bodyweight and covers over 2300 miles in as much as 86 hours.

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Seasonal migration is a kind of migration observed in birds and animals. Weather conditions often become too harsh to bear in the Arctic tundra or Arctic Canada. For this reason, animals such as the elk, moose and caribou cover vast distances to escape to more habitable regions.

Other types of migration in animals include emigration. In this, birds and animals permanently move out of an area, never to return. In general, emigration usually occurs as a result of a sudden increase in population. This is also called irruption.

Irruption, markedly, is common in smaller animals such as lemmings and locusts.

This was all about migration types and causes. For more on migration definition biology and other related occurrences, refer to our expertly-curated collection of free study material and reference notes. You can also install the Vedantu app to join live online classes.