USED BY Pigeons like other birds, Butterflies and Turles. They seem to be able to navigate solely on the Earth magnetic field. According to Quantum FFF theory, magnetic fields are just like electric fields based on monopole photonic information vector fields.
There are photon vector fields for electric negative and positive charge and for magnetic North and South potential. ( See second image of vector fields around the earth)
The boundary telescope (depicted above) is able to determine a so called fingerprint in the form of the half circle boundary shape of the two magnetic vector fields (North and South) at each location on earth. (see below).
The specific curvature of the half circle shaped boundary line (B) is the fingerprint observed to be unique for each location on earth
https://bigbang-entanglement.blogspot.com/2016/11/pigeon-orientation-by-magnetic-dual.html
https://www.flickr.com/photos/93308747@N05/albums/72157633287892650