Travis Horton at the University of Canterbury, New Zealand, plotted the migratory tracks from each species over a detailed magnetic map of Earth, which shows how the magnetic field's inclination and declination — the angular difference between the field lines and true north — vary from point to point. (newscientist.com)
Over time they build a more detailed magnetic map by learning to recognise variations in the strength and direction of the field lines, which are angled more steeply towards the poles and flatter at the magnetic equator. (newscientist.com)
Here are some of my other map posts you might like: 3D Map Star Decorations Brilliant Vintage Map Suitcase Magnetic Map Board Personalised Treat Map Heart Bags (pillarboxblue.com)