I am a pigeon fancier and I raise, train & race homing pigeons. I have heard talk about that a person can attach a "leg band" (put around pigeons leg) which has a GPS computer chip embedded in it, as the pigeon flies home you can actually watch the flight path of that pigeon, in REAL TIME on your computer monitor. What you see on the screen is a GIS map of the area in which the pigeon is flying and you watch a"RED DOT" move over the map therefore allowing you to view your pigeons flight path. You can also move the mouse over one of the red dots and it will display the pigeons band number that you previously entered this date in the program. This would be a valuable tool for me as I could watch how the pigeon flies home in turn allowing me to try other options for training the pigeons for racing season.
The only info I have read on this subject is that a "mini flight recorder" is attached on the back of the bird. This would not work for me as that device would add extra weight which would dramatically slow the pigeons speed down.