Map: An animated map created by the Cornell Ornithology Lab showing the migratory movements of 118 bird species over the course of a year. (Source: Cornell Ornithology Lab)

For the first time, scientists at the Cornell Lab of Ornithology have created an animated map showing the migrations of birds over the course of a year.

Using millions of observations from the eBird citizen science database, the map's authors were able to document the migratory movements of 118 different species. Lead author Frank La Sorte said the data offered new insights into the birds' choice of routes.

The study found that birds that head out over the Atlantic Ocean to spend the winter in the Caribbean and South America tend to follow a clockwise loop, tracing a path farther inland on their return. These circuitous routes seem to help the birds take advantage of weaker headwinds in fall and stronger tailwinds in spring.

Species that don't fly over open water tend to hew to the same narrow routes in the spring and fall, following mountain chains or isthmuses.

"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," La Sorte said.

He added citizen science like the eBird project is helping authorities make smarter decisions when it comes to conservation of species.

Curious about which species are represented on the map? Check out a numbered version here.