The Science Behind Spring Bird Migration

by Ayelen Flores, age 15

It is the time of year when birds are flying miles and miles: spring migration has started. Birds undergo a huge transformation to prepare for anything on their journey.

To prepare for migration, some birds gain weight by eating excessive amounts of food, like high-energy berries and fruits with carbohydrates. With the fat from the fruits, birds gain energy, and their internal organs shrink or grow to make room for energy-rich fat. Bar-tailed Godwits, a bird species, also increase the size of their heart and chest muscles. This improves the distribution of energy and oxygen mid-flight. A type of songbird, the Blackpoll Warbler, expands its digestive tract to process more food, then shrinks it during migration to reduce the need to refuel.

As seasons change, birds have to adapt to new habits and sleep less. While birds fly, half of their brain is asleep while the other half is awake to react to any danger. Swainson’s Thrushes sleep for nine seconds at a time. This bird also burns muscles to create energy, traveling up to 200 miles during migration in a single stretch. Burning muscles help it fly for a longer time and reduce the need to stop.

After a long journey, birds must regain organ function, shape, and refuel to create fat. Another urgent task for birds is breeding, so they have to attract mates and produce and raise chicks. However, they must work on getting food. If not, they can starve to death. Birds need to restore between 17 and 23 percent of their body weight. They also need to get protein and water.

To help migrating birds, you can grow native plants that produce berries. Adding native trees, shrubs, and wildflowers is a great way to provide natural food. Bird feeders can also help, but should be more than three feet from a window to reduce window collisions. Three and a half billion birds are killed each year by window strikes. Turning off unnecessary lights from 11 p.m. to 6 a.m. can help birds stay away from buildings on their journey. Each year, 2.6 billion birds die between fall and spring migration due to window collisions, bad weather, and a lack of resources.

[Sources: National Audubon Society; Save Our Songbirds]