Billions of birds are already on the move or about to take flight, heading back to their breeding grounds.
Why do birds migrate? It’s a matter of resources, really. “Birds that nest in the northern hemisphere tend to migrate northward in the spring to take advantage of burgeoning insect populations, budding plants, and an abundance of nesting locations,” according to Cornell Lab of Ornithology. “As winter approaches, and the availability of insects and other food resources drops, the birds move south again.”
The journey isn’t without its hazards: the stress of flying for such long clips, inadequate food, unfavorable weather. (Audubon’s Mission Migration game shows you some; can you safely navigate the birds to their destination?)