Every year, countless migratory birds travel across the globe, flying long distances instinctively without the need for maps. People often wonder, how do they know where to fly to?
According to a report from Live Science, Miriam Liedvogel, the director of the Institute of Avian Research in Germany, explained in an email that birds use various cues to maintain their migration direction.
Visual and olfactory cues are two fundamental clues birds rely on to navigate. Birds that have migrated previously are likely to remember familiar landmarks such as rivers and mountain ranges. However, birds migrating over water may lack these landmarks as references, thus relying more on their sense of smell.
Birds can also use the sun and stars as guides. Birds flying during the day use a “sun compass,” combining the observed position of the sun in the sky with their internal perception of time based on their circadian rhythm. By integrating these two pieces of information, birds can navigate their flight path much like a living sundial.
Research has shown that disrupting birds’ circadian rhythms with artificial light can lead to inaccurate navigation, highlighting the importance of the sun compass.
However, most migratory birds actually travel at night, rendering the sun’s position irrelevant. In such cases, they rely on the positions and rotations of stars, using a “star compass” to locate stars around the celestial pole. The approximate position of the celestial pole is the North Star, which humans have used for navigation for thousands of years.
Another clue birds use to determine direction is their ability to sense the Earth’s magnetic field, known as magnetoreception. This ability allows them to continue to navigate even in cloudy skies when they can’t see the sun, stars, or any landmarks.
Previous studies have found that disrupting the magnetic field can have significant effects on birds. For instance, altering the magnetic field around pigeons can disturb their homing ability.
While it is evident that birds possess magnetoreception, scientists are not entirely clear on how they accomplish this. Peter Hore, a chemistry professor at the University of Oxford, believes that birds must utilize a chemical reaction that depends on the strength and direction of the Earth’s magnetic field.
In addition to magnetoreception, birds can gather direction-related information by detecting polarized light, a type of light wave oscillating in specific, organized planes.
As sunlight passes through the Earth’s atmosphere, it undergoes predictable polarization. Birds can use specialized cells in their retinas to perceive these patterns, enabling them to understand the sun’s position in the sky even on cloudy days.
Liedvogel suggests that birds may integrate these cues, with different cues holding varying importance throughout their journey. Hore also points this out, noting that during severe thunderstorms or periods of high solar activity, the role of magnetoreception may diminish due to interference with the Earth’s magnetic field.
Furthermore, Liedvogel mentions that birds inherit their migratory habits from their parents, with the distance and direction of their flight mainly determined by genetics. Researchers like her are still investigating which genes are at play and how they function.
In addition to their navigational abilities, migratory birds possess innate long-distance flying capabilities, with their physical structure even providing aerodynamic potential.
In a previous report, a bar-tailed godwit weighing only a few hundred grams flew continuously for 11 days in 2020, covering a distance of over 12,000 kilometers from Alaska in the United States to New Zealand, breaking the world record for the longest continuous flight by a bird.
—
This news article reports on the fascinating ways migratory birds navigate during their annual journeys, utilizing various sensory cues to find their way across vast distances. From visual and olfactory clues to the use of celestial bodies like the sun and stars, birds showcase remarkable abilities in orientation and adaptation to their surroundings. Through ongoing research, scientists aim to unravel the complexities behind birds’ navigation systems and the genetic underpinnings of their migratory behavior.