If you’re a regular reader of this blog, you’ve undoubtedly heard us talk about flyways, these massive migratory superhighways upon which birds travel from South America to Alaska. This blog tends to focus on the Pacific Flyway. The concept of flyways are key not only to our understanding of migration, but to how Audubon as an organization practices conservation at scale. But it wasn’t always so clear. It wasn’t until the 1930s that a biologist named Frederick Lincoln came along and shed light on what is now bedrock to our understanding of birds and migration.

Prior to the 1920s, migration was understood from independent observation. Bird would appear in certain places at certain times of the year. And by putting these observations together, researchers had managed to patch together a general understanding that certain birds flew south for the winter, that other birds didn’t, etc. How this played out in terms of conservation was that individual habitat areas were considered independent sanctuaries.

Much of what we knew about birds at this time was gleaned from bird banding – placing a metal band on the leg of a captured bird with the location and date, which would provide some information if, at some later date, the bird was captured again at a different location. John James Audubon is largely credited with performing the first scientific banding in the modern era. With the passage of the Migratory Bird Treaty Act in 1918, the federal government assumed more responsibility for the protection of these birds, and thus found itself in need of a greater understanding of migration. It fell upon the predecessor of what is now the Fish & Wildlife Service, the Bureau of Biological Survey, to answer these questions. Lincoln, a young biologist in charge of the Bureau’s bird banding program, saw the answers in his data.

Lincoln, who had grown the banding program substantially, began to see patterns in his data that that indicated that birds generally migrated along four major flyways: Pacific, Central, Mississippi, and Atlantic. He described these flyways:

It is a vast geographic region with extensive breeding grounds and wintering ground connected with each other by a more or less complicated system of migration routes.

And he contended that this went beyond the waterfowl that were his initial focus:

There is a growing mass of evidence in support of the belief that all populations of migratory birds adhere with more or less fidelity to their respective flyways.

Sources:

“Four Flyways—What a Concept,” by Ben Ikenson

“Birds of the Great Basin: a natural history,” by Fred A. Ryser, Jr

Photo above: Frederick Lincoln at his desk, courtesy of the National Archives