Birds migrate by way of Earth’s Magnetic Field.
What other senses might humans be lacking?

At Loess Bluffs National Wildlife Refuge in Missouri every autumn, there are Pelicans. Pelicans in Missouri? Not only that, but Bald Eagles nest here, and dozens of varieties of birds from Snow Geese to Mergansers and other names I’ve never heard. Loess Bluffs is a waylay for literally millions of birds during their annual migrations.