Every birder is familiar with migration as a great time to see new and unusual bird species passing through areas where they might not be found during the breeding or wintering seasons, but how much do you really know about migration? These bird migration facts might surprise you!
- The word migration comes from the Latin migratus that means “to change” and refers to how birds change their geographic locations seasonally.
- Migration peaks in spring and fall, but in reality, there are birds migrating 365 days a year. The actual dates of when birds migrate depends on many factors, including bird species, migration distance, travel speed, route, climate and more.
- Before migrating, many birds enter a state of hyperphagia, where hormone levels compel them to drastically increase their body weight to store fat to use as energy while traveling. Some bird species may as much as double their body weight in the weeks leading up to migration.
- The time it takes a single bird to complete its one way migration can range from a few weeks to up to four months, depending on the total distance, flight speed, route and stopovers. Birds migrating late in the season typically travel faster than earlier migrants of the same species.
- Hawks, swifts, swallows and waterfowl migrate primarily during the day, while many songbirds migrate at night, in part to avoid the attention of migrating predators such as raptors. The cooler, calmer air at night also makes migration more efficient for many species, while those that migrate during the day most often take advantage of solar-heated thermal currents for easy soaring.
- Migrating birds use the stars for navigation, as well as the sun, wind patterns and landforms, all of which help guide them to the same locations each year. The earth's magnetic field also plays a part in how birds migrate.
- Birds may fly from 15-600 miles or more per day during migration, depending on when they are migrating, how far they have to go and the conditions they face along the route, including the availability of suitable stopovers.
- Transoceanic migrants – birds who follow a migration route that crosses an ocean – may spend up to 100 hours or more in the air at a single time until they come to land.
- Many migratory birds have longer, more pointed wings than nonmigratory species or birds with shorter migrations. This wing structure is more aerodynamic with less air resistance and allows for more efficient, easier flight.
- Migrating birds travel at speeds ranging from 15-50 miles per hour depending on the species, flight pattern and prevailing winds that can increase or decrease speed.
- While most migrating birds fly at heights lower than 2,000 feet, birds have been recorded migrating at up to 29,000 feet high. The height of a bird's migration flight depends on wind patterns and landforms that may create obstacles, such as mountain ranges.
- The ruby-throated hummingbird migrates from the Yucatan peninsula of Mexico to the southeastern United States every spring, a journey of 500-600 miles over the Caribbean Sea that takes 24 hours without a break.
- The rufous hummingbird has the longest migration of any hummingbird species: a one-way trip of 3,000 miles between its breeding grounds in Alaska and its winter range in Mexico. In spring, rufous hummingbirds travel north up the Pacific coast, while in autumn they travel south through more mountainous regions.
- The Arctic tern has the longest recorded migration of any bird on the planet; banded Arctic terns have confirmed a round-trip migration of roughly 22,000 miles.
- Migrating birds face many threats along their journeys, including window collisions, confusing lights that disrupt navigation, hunting, habitat loss and predation. Juvenile birds are at greater risk because of their inexperience with migration – yet somehow, birds successfully migrate every year!
Photo – Arctic Tern © Lindsay Robinson