Birder Resources

The routes followed by migratory birds are numerous, and while some of them are simple and easily traced, others are extremely complicated. Differences in distance traveled, in time of starting, in speed of flight, in geographical position, in the latitude of the breeding and wintering grounds and in other factors all contribute to great diversity. No two species follow exactly the same path from beginning to end; geographical groups of species with an almost continental distribution may travel different routes.

Bird migration is generally thought of as a north-and-south movement, with the lanes of heavier concentration following the coasts, mountain ranges and principal river valleys. In general, it may be said that the great routes of migration do conform very closely to major topographical features when these happen to lie in the general direction of the travel to be performed. It happens to work out nicely in North America where the coasts, mountain chains and come of the larger rivers do not depart from a north-and-south alignment.

(passage taken from http://www.birdnature.com/flyways.html – copyright@birdnature.com)