By Dr. Becker
There’s something inherently fascinating about migratory birds. Many travel thousands of miles to reach their warmer (and more food secure) winter homes. Their journey may take them over the open ocean, where stops are virtually impossible – not for food, water, or even sleep.
Yet their tiny bodies persevere to conquer this remarkable athletic and navigational feat. There are so many questions yet to be definitively answered… how do the birds know where they’re going and when’s the best time to leave?
And how can birds continue flying such distances without stopping, then turn around and do it again when the season changes? Not all birds make it. In fact, research suggests one-third of young birds may die from sheer exhaustion during their first migratory trip.1
This means two-thirds will ultimately triumph, and many are undoubtedly helped along by flying in a “V” formation.
Why Do Birds Fly in a V-Formation?
You’ve probably had the pleasure of looking up into the sky and seeing a flock of birds flying in a "V" formation overhead. They do this to save energy, as each bird (aside from the leader) benefits from flying in the updraft produced by another bird’s flapping wings.
Remarkably, they don’t simply position themselves behind another bird and hope for the best. When researchers attached sensors to a flock of endangered northern bald ibises, they found the birds position themselves just so, and time the flapping of their wings perfectly, in order to minimize their energy use.2
Each bird positioned itself about four feet behind the bird in front of it, at an angle of about 45 degrees. This was just the right spot to catch the rising air, or upwash, generated by the front bird’s flapping wings.
In addition, the birds timed their wing beats precisely in order to catch the upwash of the bird ahead, with their wingtips tracing the same path as well. If the movements become off, the bird will adjust its wing beat accordingly. The researchers noted in the journal Nature:3
“These aerodynamic accomplishments were previously not thought possible for birds because of the complex flight dynamics and sensory feedback that would be required to perform such a feat.
We conclude that the intricate mechanisms involved in V formation flight indicate awareness of the spatial wake structures of nearby flock-mates, and remarkable ability either to sense or predict it. We suggest that birds in V formation have phasing strategies to cope with the dynamic wakes produced by flapping wings.”
Birds Take Turns Leading the Flock
Researchers involved in the Nature study next turned to understanding how birds know which bird will lead the flock. The leading bird in a V-formation does not benefit from the upwash of a preceding bird, so must expend far more energy than the rest of the flock.
While continuing to track northern bald ibises, the researchers found the birds changed position frequently within the flock, providing the “first convincing evidence for ‘turn taking’ reciprocal cooperative behavior in birds.”4
Each bird spent an average of 32 percent of its time flying in the updraft of another bird and a proportional amount of time leading the formation. The researchers wrote in Proceedings of the National Academy of Sciences:5
“… [B]irds match the time they spend in the wake of each other by frequent pairwise switches of the leading position. Taken together, these results suggest that bald ibis cooperate by directly taking turns in leading a formation.”
The turn-taking persisted whether the birds were flying in small pairs or larger groups. Further, while you might expect there to be a few birds that chose to glide in the back and skip a turn at the lead, there were no such “freeloaders” in the group. All the birds took their turn leading the flock.
What’s the Longest Non-Stop Bird Flight Ever Recorded?
Earlier this year, the tiny blackpoll warbler was recognized for its incredible migratory journey. Researchers attached tiny tracking devices to the backs of the birds to follow their travels. It turns out the birds leave Nova Scotia and Vermont in the fall, then fly over the Atlantic Ocean to the Greater Antilles or the northeastern coast of South America for the winter.
This requires them to fly for up to three days without stops, over a distance of more than 1,700 miles. This broke the record for the longest non-stop overwater flight by a bird when body mass is factored in.6 Though remarkable, their journey looks like a quick jaunt when compared to that of the bar-tailed godwits.
The birds spend their summers in Alaska, and then migrate to New Zealand or Australia for the winter. It was long thought the birds made the trek via a series of flights, stopping along the way to eat and rest. Yet, the birds are known to feast prior to leaving, putting on so much extra weight “they looked like flying softballs,” according to biologist Robert E. Gill Jr. in The New York Times.7
For 30 years, Gill tracked the birds’ migratory flight using a series of birdwatchers he connected with along the way. When he was finally able to implant satellite transmitters into the birds to track their actual flight (which occurred in 2006), what the data revealed was astonishing. The New York Times reported:8
“Just as he had suspected, the bar-tailed godwits headed out over the open ocean and flew south through the Pacific. They did not stop at islands along the way. Instead, they traveled up to 7,100 miles in nine days — the longest nonstop flight ever recorded. ‘I was speechless,’ Mr. Gill said.
Since then, scientists have tracked a number of other migrating birds, and they are beginning now to publish their results. Those results make clear that the bar-tailed godwit is not alone.
Other species of birds can fly several thousand miles nonstop on their migrations, and scientists anticipate that as they gather more data in the years to come, more birds will join these elite ranks.”
What You Can Do to Help Migratory Birds
Migratory birds face many threats, including habitat loss and other man-made threats, like the widespread use of pesticides and other forms of environmental pollution. The Nature Conservancy, which works to protect critical habitat where birds nest, raise their young, rest during migration, and spend their winters, has put together a list of things you can do to help protect birds:9
Put up a birdhouse in your yard. Species including the purple martin, house wren, and eastern bluebird will nest in birdhouses. Put a birdbath in your yard for birds to drink from and bathe in. Use a heater in the winter if necessary. Install bird feeders and nectar feeders (place them appropriate distances from windows in locations where birds are safe from predators). Limit the use of lawn chemicals and pesticides in your garden. If birds strike your windows, apply paint or opaque tape to create a pattern on the window (with vertical stripes spaced 4 inches or less and horizontal stripes 2 inches or less), or put lightweight netting or screen several inches in front of the window. Plant native fruit and berry-bearing bushes and trees on your property. Turn off lights or close the blinds in high-rise offices or apartment buildings. Purchase forested, shade-grown, and “bird-friendly” coffee. Such plantations provide habitat for far more bird species than full sun (deforested) coffee plantations. Learn to identify common birds in your neighborhood and teach local youth to value birds and other wildlife.