Before migration, hummingbirds feed intensely. Scientists call the pre-migration feeding frenzy hyperphagia. The tiny birds spend more time than usual lapping up nectar and eating insects.  For birds about to migrate, food means survival.

When Shimmer? When Not?
When you look at an animal, it's usually easy to tell what color it is, but hummingbirds can fool us! Sometimes the hummer's throat feathers, called the gorget, shimmers with color. But other times it looks dark.

For a long time, scientists didn't know what made the gorgets of many male hummingbirds seem to change. But now they have an idea, thanks to special microscopes that allowed them to take a closer look at the feather structures.