Could be a magnetic anomaly. I watched a show on TV showing a magnetic anomaly at the site of an ancient asteroid strike. It stated when pigeons entered the area they would just fly in a circle around and around it. These were wild birds and they never said how they broke free of it.I agree they use more than one sense to get home. I do not think we will ever know for sure how they do it. Just may be one piece of the puzzle. They say the sun but I know people who have birds come in in the dark. They also say by sound. There is a place in NY called Jersey Hill near Cooperstown and almost every bird that is releases there never makes it home. They say its because of the way the land is it absorbs all kinds of sound waves. We probably will never know.
After I posted this I realized that you have to have the bird return in order to get the gps flight info.! Maybe a University would have a way to have a real time read out. ? We may never know how our birds find their way home, but something like this area should be solvable with today's technology. I hope it will happen and than we can at least know about one Boggy Man that takes our birds.That is a great idea. The reason I know about this site is because Cornell University is not far and they are trying to find out how pigeons navigate. They say when ever they let them loose in that area they loose the birds. https://www.theatlantic.com/technol...se-of-the-disappearing-homing-pigeons/272751/