Magnetoreception

Magnetoreception is the ability to sense Earth’s magnetic field and use it as spatial information. It supports orientation and navigation in diverse animals.

Cryptochrome: A light-sensitive protein family involved in circadian rhythms and, in some animals, proposed magnetic sensing. Its light-driven radical chemistry is a leading explanation for magnetic sensing in birds.
Animal migration: The regular, often seasonal movement of animals between geographic areas. Magnetic cues help many migrating species maintain routes over long distances.
Emlen funnel: A conical apparatus used to record the orientation of migratory birds from their footprints. It reveals changes in birds’ preferred headings when magnetic cues are altered.
Magnetic sense receptor: A biological structure that detects magnetic fields and initiates sensory signaling. No receptor has been conclusively established as the source of animal magnetoreception.
Sun compass: An orientation system that uses the Sun’s position together with an internal clock to determine direction. Clock-shift tests distinguish solar compass headings from magnetic compass headings.
Radical-pair mechanism: A chemical process in which magnetic fields influence reactions between pairs of molecules with unpaired electrons. It explains how weak magnetic fields might alter cryptochrome reactions and signal direction.
Bird migration: The seasonal movement of birds between breeding and nonbreeding areas. Migratory birds provide some of the strongest behavioral evidence for magnetic navigation.
Clock-shift experiment: An experiment that changes an animal’s internal clock by exposing it to an altered light-dark schedule. Clock shifts separate magnetic compass orientation from orientation using the Sun.
Magnetic sense in humans: The debated possibility that humans can consciously or unconsciously detect magnetic fields. Human magnetic sensitivity is far less firmly demonstrated than animal orientation.
Star compass: An orientation system that uses the rotation of the night sky around a celestial pole. Some night-migrating birds can orient by stars as well as magnetic cues.

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