Many birds migrate, but why do they do so? And how do they know where to go?
More than half of North American birds migrate. This is when birds move locations from where they inhabit during the summer to where they inhabit during the winter. Sometimes birds cover extremely long distances, like from Canada to South America. Others may only travel a few states south, and some even just move from a higher elevation to a lower elevation.1
Why Do Birds Migrate?
The whole point of migrating is moving into an area where there are more resources. After their breeding season, as winter approaches, resources like food might decrease. That’s why they’ll fly south to an area that has a more reliable food source during the winter.1
Many signals tell a bird that they need to get ready to migrate. Day length, temperature changes, and food supply changes are good examples of signals that tell a bird it’s time to get ready to migrate.1&2 These birds will put on more weight during this time so they have enough energy for the long and risky flight they’re about to take.2
How Do Birds Know Where to Go?
It isn’t known exactly how birds know where to go, but birds seem to be able to get their sense of direction from the sun, the stars, and from the geomagnetic field of the earth.3
Some birds migrate during the night, while others, like eagles or hawks, migrate during the day. Their preference of when they fly and, for some groups, in which formation they fly with each other, is all about saving energy and making sure they stay safe.2
Is Migrating Dangerous?
Birds face many risks when they’re migrating. Storms can be particularly dangerous for them because they can get blown off course. Threats from predators as well as man-made structures are also prevalent.2
Another risk they face is a lack of stopover sites. These birds can’t make their flight in one go. They have to stop and rest a few times as they make their way. Human interference with stopover sites can pose a major risk to birds’ ability to survive.3
Although it comes with many risks, birds need to migrate south for the winter because the resources of their summer homes get low. Then they'll move back up north when the resources are plentiful again. It's more beneficial for them to make the move twice a year because they’re actually able to have more offspring by doing this than if they stayed south the entire time.2
Check out our blog post on the importance of the Migratory Bird Treaty Act here if you missed it!