From David Quammen's article (Joel Sartore photographer) "Great Migrations", in the November 2010 issue of National Geographic:
They are prolonged movements that carry animals outside familiar habitats; they tend to be linear, not zigzaggy; they involve special behaviors of preparation (such as overfeeding) and arrival; they demand special allocations of energy.
It almost brings to mind Ziggy, who played guitar--not really, though. The word is more attractive hyphenated. I wouldn't have guessed it was a mid-19th century word.
In another magazine the above excerpt might begin: They are prolonged movements that carry animals beyond their comfort zones . . .