An average man consumes about two and a half pounds of food per day. If his energy output were the same as that of a hummingbird, he would have to eat and burn off, in a single day, the equivalent of 285 pounds of hamburger, 370 pounds of potatoes, or 130 pounds of bread. Between frequent visits to flowers, hummingbirds spend up to 80 percent of their time resting.
The ruby-throated hummingbird can increase its weight by 50 percent -- all of it fat -- just before its winter migration. This provides extra fuel for the long, nonstop flight across the Gulf of Mexico. In comparison, a 170-pound man would have to pack on enough fat to increase his weight to 255 pounds in just a few weeks.
The wing muscles of a hummingbird account for 25 to 30 percent of its total body weight, making it well adapted to flight. However, the hummingbird has poorly developed feet and cannot walk.
Due to their small body size and lack of insulation, hummingbirds lose body heat rapidly. To meet their energy demands, they enter torpor (a state similar to hibernation), during which they lower their metabolic rate by about 95 percent. During torpor, the hummingbird drops its body temperature by 30¼ F to 40¼ F, and it lowers its heart rate from more than 1,200 beats per minute to as few as 50.
Hummingbirds have the highest metabolic rate of any animal on Earth. To provide energy for flying, they must consume up to three times their body weight in food each day.
Unlike other birds, a hummingbird can rotate its wings in a circle. It can also hover in one spot; fly up, down, sideways, and even upside down (for short distances); and it is the only bird that can fly backward.
The smallest bird on Earth is the bee hummingbird (Calypte helenae), native to Cuba. With a length of only two inches, the bee hummingbird can comfortably perch on the eraser of a pencil.
This article was adapted from "The Book of Incredible Information," published by West Side Publishing, a division of Publications International, Ltd.