But they said they released the birds some distance away from their loft and then tracked their journey back. So the birds must have been driven to the release point... along that road!
Is it possible the birds were driven along that road, and they somehow have a way to simply retrace their route? Some sort of geographic memory system, maybe?
Interesting. I hadn't considered that.
That's a good question - have to check their methods. If they were like anything I saw in school, the cages were covered while they traveled and they used different routes to the release points.
Some animals have been shown to use visual cues in internal map making. I remember reading one study of squirrels and nut caching. The researchers modeled a cage with a couple trees, rocks, bushes etc and watched where the squirrels cached their nuts. Then they moved everything a meter to the left and watched where the squirrels went to retrieve the nuts when let back in the cage - all the squirrels were a meter off.
So probably the pigeons are using visual aids in their "maps" and you can't get much more visual than looking down and seeing really big lines on the ground.