As they travel, Arctic terns also use other clues such as the sun’s position and wind patterns, but their magnetic compass acts as a reliable backup. If things change, they can recalibrate and adjust their path, ensuring they always reach the right destination year after year.

During migration, they use this magnetic sense to orient themselves across long distances, from the Arctic all the way to Antarctica. It helps them stay on course, even when flying over vast oceans or through bad weather where visual cues are limited.

Arctic terns have special cells which are likely in their eyes or beaks, that let them sense Earth’s magnetic field like an invisible map. This built-in compass helps them figure out which direction is north or south, even when landmarks or the sun aren't visible.

Farther away, the sound also gets scattered by obstacles like buildings, houses, trees, and the air itself. This causes the sound to become less distinct and more muffled, making it harder to hear details like the engine’s roar or the exhaust note.

When the motorcycle is moving toward you, the sound waves get compressed, making the sound higher-pitched. As it passes and moves away, the sound waves stretch out, causing the pitch to drop lower, that’s why the engine sounds like it’s “dropping” in tone.