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:
Natural disasters.
Climate change.
Droughts.
Shortage of food.
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:
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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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?
Long distances travelled by birds and animals.
The long distances birds and animals cover in search of food, shelter and better climate.
Immigration.
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.
FAQs on Migration
1. What is migration in the context of biology?
In biology, migration refers to the large-scale, regular movement of a group of animals from one place to another and back again. This is usually a seasonal or cyclical journey undertaken in search of better food resources, more suitable climate, or for breeding purposes.
2. What are the main triggers that cause animals to migrate?
Animal migration is triggered by a combination of internal and external factors. The primary reasons include:
- Climate Changes: Animals move to escape harsh conditions, like extreme cold in winter or heat in summer.
- Food Availability: They travel to areas where food is more plentiful during certain times of the year.
- Breeding Requirements: Many species migrate to specific locations that are safe and suitable for mating, giving birth, or laying eggs.
- Predator Avoidance: Moving to a new habitat can help animals escape seasonal predators.
3. Besides birds, what are some other examples of migrating animals?
While birds like the Arctic Tern are famous for migration, many other animals migrate too. For example, wildebeest in Africa migrate across the savanna, monarch butterflies travel from Canada to Mexico, and fish like salmon swim upstream to their birthplace to spawn.
4. How is migration different from emigration and immigration?
These terms describe different types of movement. Migration is typically a two-way journey, where animals travel to a destination and later return. In contrast, emigration is a one-way movement *out* of an area to settle somewhere else permanently, while immigration is a one-way movement *into* a new area.
5. How do migrating animals navigate such long distances so accurately?
Animals use a fascinating range of natural navigation tools. Many have an internal 'compass' that allows them to:
- Sense the Earth's magnetic field to determine direction.
- Use the position of the sun and stars to guide their path.
- Recognise and follow familiar landmarks like coastlines and mountain ranges.
- Use their sense of smell to detect chemical cues in the air or water.
6. Why is animal migration important for the overall health of an ecosystem?
Migration plays a crucial role in keeping ecosystems balanced. Migrating animals help in pollination and seed dispersal as they move. They also transport nutrients between different environments. For instance, when salmon migrate from the ocean to rivers, they become a vital food source and their decaying bodies enrich the freshwater ecosystem with marine nutrients.
7. What are the biggest challenges or dangers that animals face during migration?
Migration is a very risky journey. The primary dangers animals face include exhaustion and starvation from traveling long distances, getting lost due to storms or bad weather, and increased risk of being caught by predators. Human activities also pose a threat through habitat loss and obstacles like buildings, dams, and wind turbines.
8. What are the main types of migration seen in the animal kingdom?
The main types of migration are based on the direction and reason for movement. These include:
- Latitudinal Migration: Moving from north to south, and vice-versa, to escape harsh winter conditions (e.g., whales).
- Altitudinal Migration: Moving up and down in elevation, like on a mountain, to find food or escape the cold (e.g., mountain goats).
- Reproductive Migration: Traveling to a specific place to breed or give birth (e.g., sea turtles returning to a beach).
