Outdoor America 2020 Issue 3
In 1902, the Smithsonian Institution in Washington DC coordinated the first bird-banding experiment with 23 black-crowned night-herons. Since then, in addition to extensive banding programs, researchers from across the United States have used bird-friendly GPS devices and a few have used ultralight aircraft to track migrating birds and thus unravel the mysteries of this intriguing phenomenon.
How high do birds fly? Most migrating birds fly below 2,000 feet above sea level, but some climb to 20,000 feet or higher. A bar-headed goose was once recorded at 30,000 feet above the Himalayas! Interestingly, birds tend to gain elevation the farther they travel. Birds lose weight during migration because of the distances they are traveling, which also allows them to fly higher. That’s why some waterfowl might start at 5,000 feet as they depart their breeding grounds in northern Michigan but gradually climb to 20,000 feet en route to Louisiana.
How fast do birds fly? Like airplanes, the higher birds fly, the faster they can go because there is less air resistance. Air pressure, wind speed, wind direction and time of year also affect how fast birds fly. Canada geese that depart New England in mid-November typically travel faster than those that head south in late September simply because they are migrating closer to winter when options for food and open water are more limited. With all these variables, it’s no surprise that migrating birds might fly from a pokey 10 miles per hour to more than 50 miles per hour. According to the Texas Parks and Wildlife Department, common loons are among the fastest migrants, at nearly 70 mph.
Why do birds fly in formation? Flocks often fly in a V or J pattern to be energy efficient. Each bird lets the one ahead of it cut the air, similar to two bicycle racers drafting each other. The trailing bird also catches a little lift from the air wash created by the flapping wings of the bird ahead of it. Likewise, it’s more tiring to take the front position in the formation, which is why the flock’s lead bird changes periodically.
DID YOU KNOW?
Birds can fly much higher than bats because bird lungs are more efficient at getting oxygen from thin air.
How far do birds fly? There is tremendous variation when it comes to the distance birds fly in a day and total distance during migration. Some species might go only 15 miles per day. Others log 600 miles, depending on the weather, the route, and the availability of food and shelter on the ground. Songbirds that cross the Gulf of Mexico might spend more than 100 hours aloft, then congregate in huge numbers when they finally reach land to recuperate before continuing.
How do birds find food along the way? As the time to migrate approaches, birds build stores of fat in their bodies. The species with the longest journeys or the longest periods of flight gorge the most. Some songbirds double their body weight before migration begins. They use this extra fat for fuel as they fly. That’s why backyard feeders are busy in early autumn.
Some species take a different route going south versus north due to food availability. For example, rufous hummingbirds, which migrate 3,000 miles from Alaska to Mexico and eat flower nectar, head north along the Pacific coast in the spring, and south along the Sierra Nevadas in the fall. Early blooming flowers are common along the coast in spring, whereas lateblooming flowers are more prevalent in the mountains in fall.
Do migrating birds ever get lost? Yes. Birds depend heavily on vision to find their way along a flyway. Sometimes they get caught in unexpected storms or simply heavy cloud cover and become disoriented or fly off course. They take cues from stars, the sun and land formations. Some scientists believe the Earth’s magnetic field also plays a role in how migrating birds navigate, but visual cues are key. As a result, most birds are fair-weather fliers, waiting out a storm or fog, then continuing their journey under clearer skies.