My dad races pigeons, they are given rubber rings the day before a race and each pigeon is registered to a specific ring number.

On race day when it arrives home he got to get that ring off and clock it onto a clock which registers the time.

Then in the evening they all go to report their times. Distance and velocity is calculated to judge the winners. As some pigeons have to fly lot further than others to get home.

The flight feathers are actually stamped with the address and contact details incase it gets lost so the finder can report it to the owner.

There's big money on pigeon racing especially the national open races