For the first time ever, scientists from The Cornell Lab of Ornithology have created a fascinating migration map of 188 bird species in the Western Hemisphere, capturing all of their movements for an entire year. The study uncovered the similarities in the routes used by specific species and shows each of their patterns in a unique animated map.
"We used millions of observations from the eBird citizen-science database," Frank La Sorte, lead author of the study, said in a press release. "After tracing the migration routes of all these species and comparing them, we concluded that a combination of geographic features and broad-scale atmospheric conditions influence the choice of routes used during spring and fall migration."
According to La Sorte, one of the most interesting findings of the study was that bird species that make their way over the Atlantic Ocean during their fall migration in order to reach the Caribbean and South America do so in a clockwise loop, however, on their way back in the spring, this same journey takes place more inland. Some of the species that follow this pattern include bobolinks, Cape May warblers and Bicknell's thrush.
"These looped pathways help the birds take advantage of conditions in the atmosphere," La Sorte said. "Weaker headwinds and a push from the northeast trade winds as they move farther south make the fall journey a bit easier. The birds take this shorter, more direct route despite the dangers of flying over open-ocean."
Additionally, the study reveals that although the spring migration path is a more roundabout route, the birds move at a faster pace due to the strong tailwinds that carry them north to their breeding grounds. Alternatively, for species that avoid flying over open oceans, the study reveals that spring and fall migration routes are the same.
"It's an exciting new area of research," La Sorte said. "By using eBird data and other forms of migration tracking information, we're getting a more detailed picture than ever before about where and when birds migrate. That's the kind of information we need to make smart conservation decisions for species that live in vastly different regions during the year. Citizen science makes it possible to do this for populations across an entire hemisphere."
The findings were published in the Jan. 20 issue of the Proceedings of the Royal Society B: Biological Sciences.
