Every year, billions of birds migrate to and from the United States. Around the world, these birds travel thousands of miles to reach their seasonal habitats. Some species, like the Arctic tern (Sterna paradisaea), accumulate enough miles in their lifetime to fly to the moon and back.
But how do birds find their way during these epic journeys?
They have a wide range of senses that they use to navigate – some of which are known to us, while others still remain a mystery to science.
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“We understand that birds use different signals to maintain the correct course of their migration,” Miriam Liedvogel, director of the Institute for Bird Research in Germany, told Live Science in an email.
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Sight and smell are two key cues that birds use to navigate. If they have migrated before, they are likely to remember familiar landmarks, such as rivers and mountain ranges. However, birds migrating along water routes have fewer landmarks, forcing them to rely more on smell; one study found that when the nasal passages of seabirds known as Scopoli's petrels (Calonectris diomedea) were blocked, they were able to fly over land but became disoriented over water.
Birds can also use the sun and stars to navigate. Diurnal birds use a “sun compass,” which combines the birds’ perception of the sun’s position in the sky with an internal understanding of the time of day based on their circadian rhythm. By combining these two sources of information, birds are able to determine their direction of travel, acting as a living sundial. Research shows that disruption of birds’ circadian rhythms by artificial light interferes with their ability to navigate accurately, highlighting the importance of the sun compass.
However, most birds actually migrate at night, so the position of the sun is less useful to them. In such cases, they rely on constellations and the movement of the stars to find their way. They use a stellar compass, studying the positions of the stars around the celestial pole, almost indicated by Polaris (the North Star) – the same star that humans have used for navigation for centuries.
Sourse: www.livescience.com
