Migration Station

How Do They Migrate?

Many migratory birds fly thousands of kilometres before they reach their wintering grounds. It’s a risky journey—poor weather, lack of food, exhaustion and predators are just some of the things that could go wrong.

As a result, migrating birds have evolved, both physically and strategically, to deal with these challenges en route. Here are some of the ways they cope with the many risks and difficulties of the migratory flight:

Specialization in Navigation

Birds are aware of the light and dark cycles that occur during the day. They also rely on shadows to help them determine direction. These two elements combined allow birds to use the sun as a compass.
Birds orient themselves according to the position of the stars that help to distinguish north from south. Problems arise when the sky clouds over at night. Bright city lights easily disorient migrating birds, especially songbirds.
Scientists have detected small crystals of magnetic iron oxide within the base of birds' beaks and bills. A commonly held theory is that these crystals help the birds respond to the Earth's magnetic fields. While the magnetic poles and geographic poles do differ, it is believed that magnetic fields are just another tool in a bird's migration navigation kit.
To those who have observed migrations, it is apparent that the birds follow rivers, coastlines, ridges and mountains. The types of landmarks used likely vary depending on the altitude of flight.
While many birds fly almost non-stop, still others take breaks to rest and refuel along the way. Many of these birds stop at the same key habitat areas every year, such as wetlands. Unfortunately, many of the wetland areas that were important rest stops have diminished or disappeared, making the migration trip even more difficult.

I’m Not a Chicken!

The migratory birds that are larger, faster or predatory migrate during the day to take advantage of up-swelling air currents that emanate from the heating surface of the Earth. Daylight hours also provide better opportunities to feed.
Not all migrating birds are large, fast or predatory. Many songbirds or poor flying birds (such as coots and grebes) pass on the more dangerous daylight hours and migrate at night to avoid the predators that pose such a strong threat to their survival. Flying at night during the cooler temperatures also means that the birds do not dehydrate as easily.

Up, Up and Away

Flying at higher altitudes makes for greater flying efficiency and less flying time. In fact, some migratory birds have been recorded at altitudes between 1.5 and six kilometres (5,000 to 20,000 feet).

Birds of a feather…

Many migratory birds choose to forgo a solitary trip and fly together in groups or flocks. Perhaps the most famous of these groups is the v-shaped flock of geese. While scientists do not fully understand this phenomena, there are theories that flying in a ‘v’ helps reduce air resistance, making the flight easier for the group (once the lead goose gets tired, they rotate). Scientists also believe that the ‘v’ formation helps the geese to keep track of one another and communicate.
Different species flock for different reasons. Some fly in family groups and others do it for safety from predators.

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