I have read that the Monarch butterflies have four new
generations on the way to Canada. That is why the genetically
altered corn was alleged to hurt them. The ones that go to Mexico
must have some genetic hard wired mechanism that guides them.
Magnetic particles are found in their brains, but it is only speculation
that they are part of the navigation system. For a URL

http://ufbir.ifas.ufl.edu/chap35.htm
.

Below is URL about sea turtle navigation. (forgive me if it makes screen go wide.)

http://jeb.biologists.org/cgi/content/abstract/199/1/73?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&titleabstract=turtle+navigation&searchid=1002942758853_1663&stored_search=&FIRSTINDEX=0&journalcode=jexbio