When you think of a hummingbird, you most likely think of a very small creature with furiously beating wings. No surprise that the hummingbird family contains the smallest bird in the world. Somewhat more surprising is the fact that there are more than 400 kinds of hummingbirds, 19 of which are found in the United States. It turns out that plenty of diversity can be packed into small packages; one thing all hummingbirds have in common is their ability to amaze. The smallest hummingbird is no longer than an adult bumblebee; the largest, the Giant Hummingbird, grows from 2 to 4 inches in length. Despite their diminutive stature, these birds can do many incredible things. They are the only birds that can fly backward. Their wings beat faster than those of any other bird, from 60 to 70 times per second. In the eastern United States, the Ruby-throated Hummingbird is the only kind commonly found north of Florida. While both male and female have a coat of brilliant metallic green, only the male has a bright red throat. The male is very aggressive in defending food sources, often taking on enemies much larger than himself. A mature Ruby-throated Hummingbird is only about 3 to 4 inches long. When newly hatched, three of the birds can fit inside a nest the size of a large thimble. The birds eat insects and extract nectar from flowers for their diet. Many people hang hummingbird feeders containing sugar water, and hummingbirds flock to them. Feeders are an important supplement to their natural diet. Although they weigh as little as a penny, they have long migration routes to follow in spring and fall. They are marvels of speed, agility, and beauty. Which of the following sentences best summarizes the passage?