How Birds Migrate Throughout the Western Hemisphere (2018)

To conserve energy, migrating birds often take direct—and dangerous—routes, which can expose them to storms, predators, and disorientation from perilous navigation conditions. On rare occasions, a storm front or band of rain intersects the birds, killing thousands and forcing an entire sky full of them to stop at the first land they encounter. Habitat loss, pesticides, and hunting or trapping on stopover grounds have taken major tolls on migrating birds.

Source: www.nationalgeographic.com