Read the text about the migration of birds and find the words to be explained below the text.
Science – Learning About Migration
Animals, birds, fish, insects, and even humans migrate. Since migration takes a lot of time and energy, they must have really good reasons to do so. Today, we are going to look at the migration of birds, to find out why they migrate, where they go to and how they get there.
Most migratory birds migrate seasonally. When the weather starts getting cold and it becomes more difficult to find food, or open water, many northern birds fly south. They return in spring and summer to breed. If you live quite far north, you will know that the first spring visitors to our gardens are usually the robins and the starlings. Although individuals of these species sometimes spend the winter with us and enjoy any tidbits, we put out to see them through the cold weather.
Birds can usually tolerate cold temperatures as long as there is food available. That is why some birds, like the chickadees, which change from eating insects to eating seeds in winter, don’t have to migrate.
Most ducks, geese and shore birds migrate south in large numbers during fall. You can often see and hear the geese fly over in V shapes, honking as they go! Some of them fly extremely high. Bar-headed geese, for example can reach 29,000 feet, that’s even higher than Mount Everest!
Some birds are short distance migrants; they only travel as far as they have to in order to find food. Others, like the arctic tern fly long distances. The tern flies from the Arctic, where it breeds, to the Antarctic and back every year. This is a distance of about 30,000 km (18,600 miles). Most birds have stopover sites where they rest and eat, sometimes for a day, sometimes for weeks, before moving on again.
Learning About Migration
Birds migrate by day or by night. Birds of prey, swallows and crows, for example, migrate by day while most songbirds migrate at night. They find their way to their destination in a number of different ways:
They can navigate by the sun or the stars.
They have very good vision and watch for landmarks, such as mountains and rivers.
Birds like petrels and pigeons can also use their sense of smell. ''
But perhaps the most interesting navigation device they have are tiny grains of a mineral called magnetite which is found just above their nostrils and which scientists think may act like a compass, telling them which way to go.
No comments:
Post a Comment