Bird migration is a monumental and mysterious process — especially given that most birds fly solo and overnight.

Migration behavior varies across bird species, and it’s presumed to be at least partly inherited. The Earth’s magnetic field is thought to be another factor that helps birds migrate so precisely.

Amazingly, quantum mechanics may play a role too. Simply put, unpaired electrons, or free radicals, in cells have a property called “spin,” which is especially sensitive to magnetic fields. Light is one way to stimulate free radical production, and a protein called cryptochrome 4 is important as well. That protein is higher in migrating versus nonmigrating birds.

It’s all too complex to fully cover here, but it sure gives the term “bird brain” a whole new meaning.