We are deep in the throes of one of nature's greatest mysteries. Migration simply defined is the seasonal movement of animals from one habitat to another. In this context, the common movement of elk from their high, summer breeding grounds, down to more hospitable winter habitat is easy to comprehend. The motivation for migration, whether it be from mountain top to bottom or half way around the globe, appears to be the same.
Migration allows animals the opportunity to take advantage of seasonal resources.
Waterfowl take advantage of the long summer days, abundant forage, and relative scarcity of predators to nest and raise their young, in the northern reaches of the tundra. As autumn approaches the tundra days begin to shorten, the temperature begins to fall and the abundant food supply begins to disappear. The waterfowl gather in large flocks and head for the more accommodating swamps, marshes and flooded croplands of the south. While the trigger mechanism for migration may remain the same, the logistics become more and more difficult to ascertain when biologists begin looking at the grand scheme. When we speak of the mechanics of migration we have to speak in the broadest sense because there are so many variables.