Birds' ability to fly allows them to travel long distances. They can do this more quickly, more safely, and using less energy than animals that have to walk. That is why so many different kinds of bird migrate. Some insects migrate too, even though their smaller size makes the journey more difficult. Among non-flying land animals, only a few undertake long-distance migrations. They are usually large mammals such as the caribou.

Why do birds migrate?

Migration takes a lot of energy, and it is dangerous. The birds have to pass through a lot of unfamiliar places. Many die along the way. Food supply is the main reason birds make such long, hazardous trips. If birds stayed south all summer, they would have to compete with other southern birds for the limited supply of food. This would be especially difficult when it came time to feed a nest full of hungry chicks. By travelling north in the summer, birds find good habitat with fewer competitors than there would be if they all stayed in the south.

Not all birds migrate. Some live in the tropics year-round. Others stay in the north all year. Birds that don't migrate are those that can tap into a particular food source that's available year-round. For example, woodpeckers can dig into the bark of trees where many insects spend the winter.

How do birds migrate?

Birds store up extra body fat, which gives them the energy for the trip. The fat can be up to fifty percent of the bird's body weight when it sets out on its migration flight. Most birds stop to eat during the migration, but they still rely on stored fat to make it through. It can be hard to find food when travelling through unfamiliar areas. Some birds fly at night when they migrate. Others fly during the day. Birds try to use weather patterns to assist their migration flights. For example, they will wait for a tail-wind before starting out on migration. This way, they can complete the trip faster and save energy.

How do birds find their way?

Birds can sense the Earth's magnetic field, and they use a variety of visual clues such as the stars and land features to help them navigate. Although many birds have an instinctive urge to migrate, birds learn their specific migration route the first time they make the trip south with their parents.

This created a problem when biologists wanted to establish a new population of the whooping crane, an endangered species. Biologists were able to raise the whooping cranes in captivity, but the cranes would not migrate! Biologists taught the cranes to follow a small, manned airplane called an ultralight. This plane led the birds on their thousand-mile journey from Wisconsin to Florida, and after that first time, the birds knew how to make the trip on their own. more

Notable Migrants

Arctic Tern. This bird migrates over 20,000 miles each year, flying from the arctic to the antarctic and back. No other species travels farther. more

Bar-Tailed Godwit. This bird, related to sandpipers, makes the longest non-stop migratory flight. It flies 7,000 miles over the Pacific Ocean from Alaska to New Zealand! The trip takes five or six days. more

Monarch Butterfly. Best-known of migratory insects, the monarch butterfly travels from the US and Canada to Mexico, where it spends the winter. Individual monarch butterflies never complete the return voyage. They lay eggs, and their offspring continue northward to lay more eggs, so by the end of summer monarchs have repopulated much of the continent. more

Snow Goose. The snow goose is famous for congregating in huge flocks during its migration from the arctic to the southern US. As many as a million of these beautiful white birds can be seen in one place!

Video: Snow Geese in New York State