Hummingbirds are fascinating creatures for many reasons. They often have feathers in bright colors, and move so quickly that the iridescent colors seem to catch and reflect the sunlight. Hummingbirds can fly in any direction, including backwards, beating their wings up to 80 beats per minute. As they hover in midair, they can drink nectar from flowers through their long beaks. Because hummingbirds dart and fly so fast, they expend excessive amounts of energy. This makes it necessary for them to eat at least half their body weight every day to replace their expended calories. Generally, hummingbirds spend their waking hours eating, possibly visiting more than 1,000 flowers each day. The tiniest hummingbird is the bee hummingbird, which weighs less than one ounce and is only two inches long. The ruby-throated hummingbird is usually three to four inches long, and weighs less than 0.2 ounces. Hummingbirds generally migrate each autumn to winter in Mexico or Central America. This migration involves a nonstop flight of 600 miles as the birds cross over the Gulf of Mexico. Hummingbirds usually spend the latter half of the summer eating to prepare for migration. Then, in the spring, they return north when the flowering shrubs and plants bloom once again.