When 80,000 doves spread their wings and flew across Beijing's Tian'anmen Square on September 3, it was a poignant moment that conveyed a message of peace to the world.

This spectacular display was made possible by many months of preparation. The doves were all on loan from the Beijing Pigeon Association and had undergone health screening and systematic training before being enlisted. Thanks to their strong homing instinct, all the birds returned safely to their original owners after their epic flyover.

But just how do so many birds find their way back home on a day of such mass celebration?

Homing doves use magnetoreception, or the ability to sense the Earth's magnetic field, for navigation through two primary systems: a light-dependent mechanism involving photoreceptors containing cryptochrome in their eyes, and a magnetite-based system located in the upper beak region. The visual system uses radical pair chemical reactions to act as a compass, while the magnetite-based receptors likely provide information about magnetic intensity to create a navigational "map."

Birds can also use the celestial system comprising the Sun, Moon, planets and other celestial bodies for orientation. Unlike the geomagnetic field, the sun's position varies daily, with latitude and with the seasons. Birds rely on their internal "biological clocks" for solar orientation.

Over time, doves learn to recognize familiar visual cues and landmarks to guide them home. In a similar way to how we find our way, birds memorize prominent geographical features such as rivers, mountains and buildings during flight. These familiar landmarks help homing doves to improve their navigational skills and return home quickly.

Furthermore, birds accumulate experience over time. From the time they are chicks, following their parents on their migrations strengthens their memory of migratory routes.