The Mystery of the Migration Route
Do birds fly the same route on migration in spring and fall? Would it surprise you that many of them don’t? In fact, scientists are finding out that many birds, especially in spring, follow a path of new plant growth — what is called a “green wave” of migration — where birds follow patches of insects and food going north. In fall, especially in the western US, they take a more direct route south, staying at higher elevations, creating a round trip route that looks like a loop for their migration as opposed to a straight line used both directions. For birds in the western US, it might seem to us to be a less enticing route, but if the choice is flight over desert, or flight over wilted foliage with insects in it, the choice seems fairly straight forward.
This “looped migration” offers conservationists the opportunity to fine tune their efforts to benefit birds on migration by building, preserving and reinforcing stop-over habitats where they are needed.
The information which went into this study has been made possible by birders like you who post sightings on ebird, which helps create a database of bird sightings over time. See more on this interesting discovery at Cornell Lab of Ornithology.