how do they do it

Homing Pigeons
1. The homing pigeon comes from the family of "Columba livia domestica," or Rock pigeons. These birds have been bred to find their way home from long distances, as wild rock pigeons always return home to their nests. Homing pigeons can fly as fast as 30 mph, with small bursts of speed as fast as 55 mph. The longest flight ever recorded in pigeon racing was over 1118 miles (1800 kilometers).

Sometimes homing pigeons are used to carry messages. In this case, they are called carrier pigeons. Messages are written on the lightest paper possible, rolled into small tubes and tied to one of the pigeon's legs.

Homing pigeons, which are sometimes white, are also frequently used in place of doves in ceremonies such as weddings and sporting events where they are released for dramatic effect.
Using the Earth's Magnetic Field
2. Scientists have always known that homing pigeons use the Earth's magnetic field to navigate, but it wasn't until 2007 that scientists discovered minute, iron-containing particles of maghemite and magnetite in the branches of nerve cells in the skin of the upper beak of homing pigeons. These branches are arranged in a three-dimensional pattern that allows the pigeon to analyze all three parts of the magnetic vector field, much like a three-axis magnetometer.

Homing pigeons can analyze the magnetic field regardless of how they are moving, therefore identifying their position. Homing pigeons use this skill when traveling long-distances, even for the first time.
Using Familiar Landmarks and Roadways
3. Homing pigeons navigate in another way as well. When traveling short distances or longer, more familiar routes, homing pigeons use ground landmarks. This often includes roads. Studies of homing pigeons show that these birds will follow the line of a road, even going around roundabouts, when they are traveling familiar routes close to home.

Pigeons also use the position of the sun, comparing it to their internal clocks. They have also been known to use the stars and the moon to find their way. Even when skies are overcast, they can still find their way home, although usually more slowly. Finally, homing pigeons have also shown that they have the ability to smell "home," although not from long distances. It is thought that the extent to which these different methods of finding their way home are used varies a bit, depending on the pigeon's breed.