Migratory birds follow routes between their breeding and wintering grounds. While these routes initially appeared very simple (and following a general north-south movement), as more data is collected people are realizing that migration and the routes used are often more complex than first thought. Birds do, however, generally follow major landmarks such as major river and their valleys, mountain ranges, and coasts. In North America, these topographical features happen to run...you guessed it...north-south!
So what exactly is a flyway? During the 1930s, bird banding data started to be collected and plotted. This data, when looked, at revealed what appeared to be 4 major, general and broad pathways used by migrating birds. These lent themselves readily to use in a more administrative sense. I guess you could think of a migration route as pathways of individual movement from one breeding area or ground to areas that birds go for winter; flyways are broader areas and related migration routes can and often do become overlapping and blend together in a defined geographic area. Flyways are giant multi-laned highways that the routes feed into. Make sense???
Alright...hopefully I didn't just confuse you! The Atlantic Flyway covers the eastern United States from offshore in the Atlantic (where pelagic species travel with few to witness them) to the Allegheny Mountains and actually curves northwesterly to include prairie provinces of Canada, the Northwest Territories, and over to the Arctic coast! These routes in the flyway are essential for some birds such as Lesser Scaups, Canvasbacks, and Redheads that winter on marshes found just south of the Delaware Bay.The coastal portion of the Atlantic Flyway generally follows the shoreline and originates in the eastern Arctic islands and Greenland's coast.
Many birds will go from the panhandle and northwestern Florida region across the Gulf of Mexico to eastern Mexico. There they have a land route for the rest of their migration. However, many take a different route. Migrants taking this way will leave the coast of Florida and fly south to Cuba. Over 60 species of migrants go this way! Around 30 of these will stay in Cuba for the winter while some fly 90 miles south to Jamaica. Some stay in Jamaica and a few brave the perilous 500 miles of unending water to the northern coast of South America. Others may veer to follow and spread out amongst other Caribbean islands.
Birds (and other animals)do not recognize arbitrary man-made boundaries so cooperation amongst many agencies and countries is essential for a migratory bird species continued survival. These flyways allow for this cooperation to be more concise and quantified.
Yellow-throated Warbler in Spanish moss