1/ Fun fact: humans aren't the only species on Earth that learns the patterns of stars in the sky. The Indigo Bunting learns the star patterns as a chick and uses them to find direction for migration the rest of its life. (Photo by Dan Pacamo commons.wikimedia.org/wiki/File:Indi…) 
2/ Cornell researcher Stephen Emlen raised indigo buntings and performed experiments with them in a planetarium. The chicks observed the sky full of stars rotating overhead in the planetarium and learned the direction to the center of the sky's rotation -- the North Star.
3/ Emlen could rotate the entire artificial sky inside the planetarium, so the North Star could be in any direction he wanted. When it came time for the birds to migrate north, they flew toward that North Star, proving it was actually the view of the stars that they followed.
4/ They weren't following Earth's magnetic field or some internal compass of another sort. They were literally looking at the sky, learning the patterns of the stars, and flying north based on the constellations. Likewise when it was time to fly south, they followed the stars.
5/ The stars are not hard-wired in birds' brains. The stars move slowly in the sky. The Big Dipper once didn't exist. A few thousand years ago, Polaris wasn't the North Star. Every generation of birds has to learn for itself the sky that it sees. (Credit: Tauʻolunga/Wikimedia)
6/6 I didn't know this, but I stumbled upon it as I was learning how humans develop concepts (like "what is a planet?"). You can read more about the fascinating experiments of birds flying inside planetariums via the original research paper, here: ntrs.nasa.gov/archive/nasa/c…
