Ask Mr brain..all will be explained

PUBLISHED : Wednesday, 07 April, 1999, 12:00am
UPDATED : Wednesday, 07 April, 1999, 12:00am

How do birds know which way to go when they migrate? MIMI KAN Sacred Heart Canossian College Some birds, like many other animals, migrate to find suitable places to breed or new food supplies. The Arctic tern travels up to 40,000 kilometres each year in the course of its migration between the Arctic and the Antarctic. This makes it the animal with the longest migration route.

But since there are no maps for birds, how do they know where to go? Birds use several methods of navigation, some of which are still not fully understood. Like humans, sometimes they use landmarks, following rivers or coastlines to their destination.

Some birds seem to have a built- in 'compass' which they use in conjunction with the sun, moon or stars to navigate. Since migrating birds sometimes get lost on very foggy nights, scientists say this is evidence that they use the stars or moon to help them navigate.

It is also thought that some birds use the Earth's magnetic field to help them find their way across oceans. While humans cannot detect the Earth's magnetic field, birds can and are able to sense which direction the force is aligned. Since the way the force is aligned varies from place to place, it could be used to help navigation. While scientists do not understand how birds navigate, it is clear that the methods they use are accurate and efficient, enabling them to return to the same areas to spend winter thousands of kilometres from their summer sites.

Which is the largest rainforest in the world? The Amazon rainforest of South America is larger than all the other rainforests put together and is twice the size of India. The vegetation is dense and tall and little light reaches the forest floor.

Almost half the world's bird species are found there, including more than 300 species of hummingbird. The many forest animals include sloths, jaguars, tapirs, snakes and countless insects.

Rainforests grow near the Equator, where it is warm and wet all year round. This climate is ideal for plant growth and, as there are no seasons, rainforest trees are evergreen. Animals feed and shelter at all levels in the forest, helping to pollinate the trees' flowers and spread seeds.

The West Coast of the United States is an active earthquake zone. Why doesn't the East Coast have more quakes? Earthquakes occur fairly frequently along the West Coast of the US because that's where two of the Earth's huge tectonic plates come together. The movements of these plates against one another account for the earthquakes.

But earthquakes aren't entirely unknown in the eastern part of the country. Northeastern North Ameri ca has shaken more often than most people realise, with tiny quakes taking place regularly in many areas.

A large tremor, felt as far away as New York and Chicago, struck Charleston, South Carolina, on August 31, 1866, killing 60 people and damaging some 2,000 buildings.