Homing pigeons find their way by following roads. Scientists had thought that they use the position of the sun to determine direction. Apparently not, as documented in this Daily Telegraph article entitled "How Do Homing Pigeons Navigate".
I'm somewhat dissatisfied with this answer. In science it is always important to know what the axioms or primitives are of the research. In this case, how did people know homing pigeons existed before there were large road nets? What did they home by when there were no roads?