Radiolab Episode: Internal Compass and Bird Migration
Introduction
Host: Latif Nasser
Focus: Follow Annie McEwen, senior producer, on her quest to understand bird migration.
Location: Hawk Mountain Sanctuary, Pennsylvania, to catch and study northern saw-whet owls.
Northern Saw-whet Owls
Smallest owl in the East, about the size of a soda can.
Described as "cosmically cute," weighing slightly more than a robin.
Catching method involves setting up nets and playing recorded mating calls.
Purpose of Owl Study
Owls are migrating creatures.
Tagging allows researchers to study lifespan, travel patterns, and mating habits.
Personal Interest: Bird Eyes
Annie's interest in a bird's eye stems from the idea that it may hold answers to big biological mysteries.
The Mystery of Bird Migration
Birds can migrate vast distances without traditional navigation tools.
Use multiple methods: stars, sun, landmarks, smell, and sound (low-frequency waves).
Earth's Magnetic Field
Birds likely use Earth's magnetic field for orientation.
Historically believed to involve magnetite crystals in bird beaks.
Issue: Magnetite isn't linked to bird brains, questioning this theory.
New Hypothesis: Quantum Mechanics
Klaus Schulten and Radical Pairs
In the 1970s, Klaus Schulten proposed a theory involving radical pairs and quantum mechanics.
Radical pairs: entangled electrons that can remain connected and sensitive to magnetic fields.
Schulten's idea was initially rejected due to its complexity and fragility in biological environments.
Revival of Schulten's Theory
In 2000, Thorsten Ritz revisited and simplified Schulten's hypothesis.
Cryptochrome, a pigment in bird eyes, can create radical pairs when hit by light.
This discovery aligned with Schulten's hypothesis, suggesting birds might see magnetic fields.
Quantum Mechanics Explained
Quantum world defies traditional rules: particles exhibit strange behavior such as entanglement.
Radical pairs in the bird's eye become magnetically sensitive, potentially forming a chemical compass.
Bird's Visual Perception of Magnetic Fields
Birds might visually perceive Earth's magnetic field, a landmark in their vision.
Likely more vivid due to birds' tetrachromatic vision (four color channels).
Annie McEwen's Field Experience
Witnessed owl capture and study.
Release of tagged owls after documentation.
Reflection on the extraordinary capabilities of birds.
Conclusion
The episode intertwines bird migration with quantum physics, offering a speculative but fascinating explanation of how birds may navigate using Earth's magnetic field.
Scientists continue to explore this intersection of biology and quantum mechanics.