UNIT

8Ecosystems III: ecological balance

Biology & Geology. Secondary Education, Year 4

MIGRATION AS A MECHANISM OF SELF-REGULATION

UNIT

8

Biology & Geology. Secondary Education, Year 4

Migration as a mechanism of self-regulation

The migration of birds

• Migration is the yearly, seasonal journey undertaken by many species of birds. During this journey, birds can cover distances of many kilometres.

• The most common types of migration are those carried out by birds in spring and autumn. In the autumn they travel from the mating or breeding grounds in the north to the wintering grounds in the south, and vice versa in the spring. .

Breeding groundsBreeding grounds

Wintering grounds Wintering grounds

Autumn migration

Spring migration

Large birds, like geese and birds of prey, tend to migrate during the day.

Black geese flying in a V-formation

But smaller birds, like robins, migrate at night.

Robins

The migration of birds

UNIT

8Migration as a mechanism of self-regulation

Biology & Geology. Secondary Education, Year 4

Birds that migrate are called migratory birds, while birds that remain in the same area are called sedentary birds.

The migration of birds

Geese are migratory birds. A sparrow is an example of a sedentary bird.

UNIT

8Migration as a mechanism of self-regulation

Biology & Geology. Secondary Education, Year 4

Why do birds migrate? • Birds depend on the amount of food available in an area to survive and raise their chicks, so when food is scarce in one area, they move to areas where it is more abundant. .

• Changes in the amount of food available in certain areas are related to changes in temperature. These changes occur in different seasons in different regions of the world. .

NORTHAn abundance of food in the summer.Shortage of food in winter.

SOUTHAvailability of food all year round.

Spring Autumn

UNIT

8Migration as a mechanism of self-regulation

Biology & Geology. Secondary Education, Year 4

Bird migration routes

• Migratory birds follow the same migration routes every year. .

• Birds that migrate from Northern Europe to regions further south of the continent to spend the winter are called wintering or pre-Saharan birds (they do not cross the Sahara Desert).

• Birds like geese or cranes come to the Iberian Peninsula from Northern Europe to spend the winter here. .

Sahara

Crane migration

Crane

UNIT

8Migration as a mechanism of self-regulation

Biology & Geology. Secondary Education, Year 4

Birds that migrate from Africa to Europe to breed during the summer are called summering or trans-Saharan birds (they cross the Sahara Desert).

Bird migration routes

The swallow is a typical example of a trans-Saharan bird.

UNIT

8Migration as a mechanism of self-regulation

Biology & Geology. Secondary Education, Year 4