9 Fascinating Insights Into Bird Migration

Long-distance bird migration stands as one of nature's most breathtaking phenomena—but the story behind how we came to understand it is nearly as extraordinary as the migrations themselves. My book, Flight Paths: How a Passionate and Quirky Group of Pioneering Scientists Solved the Mystery of Bird Migration, unveils that story, showcasing the ornithologists, engineers, and researchers who dedicated their efforts to uncovering the secrets of migration and the innovative techniques they created to study it. Below are nine fascinating facts about migratory birds and the people who research them.

1. An early theory about bird migration suggested that birds were flying to the moon.

In the 17th century, minister and educator Charles Morton put forth the theory that birds were traveling to the moon and back when they vanished and returned with the changing seasons. While this idea might seem outlandish today, some of his guesses were surprisingly accurate—he proposed that shifts in weather and food availability could drive birds to seek out better (perhaps even lunar-like) habitats, and he even speculated that birds' body fat could help them survive the long journey.

2. The Pfeilstorch provided the first solid proof of intercontinental migration.

In 1822, a German hunter shot a stork that had a large spear lodged in its neck. Investigation of the spear’s wood and iron confirmed it was made in Africa, proving that the ill-fated bird had traveled across continents before meeting its untimely demise. The famous stork, known as the Pfeilstorch (meaning 'arrow stork' in German), is still on display in the University of Rostock’s natural history museum in Germany.

3. Researchers once attempted to track migratory birds by ‘moon-watching.’

Before the digital age, scientists had to get inventive to track migrating birds. One early approach involved “moon-watching,” where telescopes were used to count the dark shapes of birds flying across the full moon [PDF]. Another method was recording the calls of birds overhead—during the 1950s, two scientists created a makeshift recording system using bicycle axles to hold 6000 feet of tape, allowing them to capture eight hours of bird calls [PDF].

4. Birds employ various methods to navigate during migration.

Studies involving birds in planetariums have shown they can orient themselves by the stars. The sun's position during the day, visible landmarks, and even some genetic wiring all play a part. Additionally, there is strong evidence that birds can detect the Earth's magnetic field alignment—though the exact mechanism remains unclear, it likely involves quantum physics.

5. Migrating birds undergo remarkable physical transformations.

Long-distance migration demands immense energy, so birds preparing for long journeys accumulate extra body fat, sometimes doubling their weight before migration. Their hearts and flight muscles grow to provide the necessary power, while many of their internal organs shrink temporarily, with some digestive organs being reabsorbed until they’re needed again. In extreme cases, birds may even burn their muscles for energy when fat reserves are depleted.

6. The longest nonstop bird migration in the world spans from Alaska to New Zealand.

In 2007, a bar-tailed godwit—about the size of a football—was fitted with a satellite transmitter while on its breeding grounds in Alaska. This device allowed scientists to track the bird, nicknamed E7, as she started her fall migration. She flew non-stop for eight days, crossing more than 7000 miles of the Pacific Ocean, before landing in New Zealand. In November 2022, another bar-tailed godwit was tracked as it completed a non-stop journey of over 8000 miles from Alaska to Tasmania.

7. Not all bird species migrate.

While birds are widely known for migrating, not all of them do. Migration allows birds to exploit the resource surges that occur at different times of the year in various parts of the world. However, it also poses significant risks, including physical strain, food scarcity, predators, extreme weather, and other dangers. Only about 40 percent of the world’s bird species migrate, with the remaining species staying in their habitats year-round.

8. Modern scientists have access to cutting-edge tools for studying migration.

Technological innovations from the past century have been extensively utilized to track bird migration. Today’s researchers monitor birds’ movements using a range of tools including weather radar, high-volume genetic sequencing, isotope analysis, and even artificial intelligence.

9. Migratory birds face significant challenges (but you can make a difference).

A pivotal study released in 2019 revealed that North America now has 3 billion fewer birds than it did in 1970, representing a nearly 30 percent decline. However, the researchers provided a list of seven simple actions that anyone can take to support bird populations, such as keeping pet cats indoors, planting native plants in your garden, opting for bird-friendly coffee, and reducing plastic consumption.