How Birds Navigate the Night Sky

Learn the Secrets of Bird Migration!

Oct 18, 2017
Migratory Birds

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How do birds know where to migrate to without getting lost? How do they navigate the dark night sky? Read on to discover the secrets of bird migration!

In autumn, millions of songbirds migrate at night to their winter homes in Central and South America from breeding grounds in the northern United States and Canada.

Warblers, thrushes, and buntings are just some of the species that are night migrants, and occasionally these birds can be observed (with the aid of binoculars) crossing the full Moon. Birds leave as soon as the Sun sets; peak migration is between 11:00 PM and 1:00 AM at altitudes of 2,000 to 5,000 feet—with some flying as high as 21,000 feet.

Navigating the Night Sky

In the 1960s, German ornithologists Franz and Eleanore Saver discovered that birds navigate the night sky by using the stars. A decade later, a Cornell scientist was able to identify the specific star patterns used by the indigo bunting. For indigo buntings, orientation to the night sky develops as the young birds observe the stars. When star patterns are reversed in a planetarium, buntings will change their orientation 180 degrees, showing that they use the stars to guide themselves.

While they are programmed to orient to the North Star (Polaris), they require a rotating sky to first obtain a fix on Polaris. Stars have fixed positions, but since Earth rotates on its axis, the sky appears to be rotating. Polaris is stationary, however, and Cornell scientists determined that buntings can orient from Polaris or other constellations within 35 degrees of Polaris, especially the constellation Orion.

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Earth’s Magnetic Field and the Sun

Birds migrating by day use the Sun to navigate, adjusting their angle to the Sun as the Sun’s position moves from east to west.

Some birds, like robins, use Earth’s magnetic field to assist in migration. It is believed that they have magnetic crystals near their nostrils to help them sense the field and orient themselves. Birds also use landmarks such as islands, trees, and buildings, as well as sounds and smells, when they search for nesting grounds in spring.

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Credit: Cephas CC BY-SA 3.0

Spotlight on the Blackpoll Warbler

The blackpoll warbler, which nests in northern New England and Canada, makes the longest migration of any North American songbird. Headed to South America, this warbler makes an 88-hour flight from Maritime Canada and Maine directly over the Atlantic Ocean to the Amazon, a nonstop flight of some 2,200 miles. In the weeks before making this flight, they more than double their weight by gorging themselves on insects and berries.

Near Bermuda, flocks can reach sizes of up to 1,000 birds as they take advantage of northeast trade winds. They increase their altitude to 15,000 feet—and sometimes to as high as 21,000 feet—where the air is calmer. They finally drop to land near Aruba.

This flight over Bermuda was discovered not by using radar, but by an ornithologist sitting by the pool in Bermuda on a September evening and recognizing the distinctive call notes of hundreds of blackpoll warblers in the sky.

So, keep your eyes and ears pointed toward the sky this season—you never know what fascinating birds you may discover overhead!

About This Blog

Tom Warren has had an interest in birds since the age of 3, when he lived across from the President of the Massachusetts Audubon Society, who showed Tom how to care for injured birds. Later, a neighboring grandmother taught him the songs of warblers and thrushes, and in the eighth grade, his Middle School biology teacher took his class on birding excursions every weekend. Tom has guided bird walks and owl prowls for conservation groups, and has also participated in annual Christmas Bird Counts and the Hawk Watch on Pack Monadnock Mountain. Throughout the years, he has spent time at Pt. Pelee in Ontario observing the spring migration and has traveled to a variety of other migration areas. Tom is also committed to protecting birds and their habitat as a Trustee for both Massachusetts and New Hampshire Audubon, and the Harris Nature Center.

Reader Comments

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Bird Migration

We live on the extreme North Shore of Long Island. Our beach has a brackish pond on one side of it, so we get to see all kinds of water fowl and migrating birds. The water fowl love the Sound side for the salt water, and many other birds enjoy the calmer and less salty waters of the pond. Part of it is designated a preserve, so they are also safe there. Monarch butterflies love the goldenrod and Michaelmas daisies that blossom there as well, so we get to see a variety of migrating critters every fall.

Bird Navigation

I found this fascinating. I have always wondered about birds and how they seem to know just where to go and when to do it. I've especially wondered about flight time and whether or not they stop to rest each day or just fly straight through. You have answered many questions. Thank you!

Astronomer Comment

Glenn, I used data on Polaris from an article in American Birds which quoted a Cornell ornithologist (formerly at the University of Michigan), Stephen Emlen. His research was done in the 1960's.

Bob Berman confirmed your correction. Thank you for taking the time to correct the data.

Tom

Little birds’ migrations....

It is so amazing to know that such tiny, tiny birds fly nonstop 2,200 miles to get to where they’re going!!!!!.....AND BACK later on!!!!!!!! I am completely awed by that!!!!! That’s truly a stunner in the animal world!!!!!!! All I can say is......WOW!!!!!!!!

How Birds Navigate the Night Sky

I enjoyed reading your article on the secrets of bird migration. In it you say, “Cornell scientists determined that buntings can orient from Polaris or other constellations within 35 degrees of Polaris, especially the constellation Orion. “ As an astronomer I have to point out that no part of that constellation is any closer to Polaris than about 67 degrees. The northernmost bright star in Orion, Betelgeuse, is about 82 degrees away from Polaris! You might want to check with the Almanac’s resident astronomer, Bob Berman, about all of this. Regardless, birds …and stars …are a wonder.

Migrating birds

What a fascinating article! I always learn something interesting on this website. Thanks!

So fascinating! Birds are so

So fascinating! Birds are so amazing!!!

Bird Migration

Very interesting article!

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