Hummingbirds are birds comprising the family Trochilidae. They are among the smallest of birds. They can hover in mid-air by rapidly flapping their wings 12–90 times per second (depending on the species). They can also fly backwards, and are the only group of birds able to do so. Their English name derives from the characteristic hum made by their rapid wing beats. They can fly at speeds exceeding 15 m/s (54 km/h, 34 mi/h). The Giant Hummingbird's wings beat at 8–10 beats per second, the wings of medium-sized Hummingbirds beat about 20–25 beats per second and the smallest can reach 100 beats per second during courtship displays.
With the exception of insects, Hummingbirds while in flight have the highest metabolism of all animals, a necessity in order to support the rapid beating of their wings. Their heart rate can reach as high as 1,260 beats per minute, a rate once measured in a Blue-throated Hummingbird. They also consume more than their own weight in nectar each day, and to do so they must visit hundreds of flowers daily. Hummingbirds are continuously hours away from starving to death, and are able to store just enough energy to survive overnight.
Source: en.wikipedia.org/wiki/Hummingbird - 30.09.2010
Hummingbird and Cactus
With many species of Hummingbirds the plumage glimmers metallic-green.