The smallest hummingbird is the Bee hummingbird of Cuba. This little fellow weighs only 1.95 grams.
The fourth smallest hummingbird, the Calliope comes in at 2.5 grams. These are tiny birds.
Hummingbirds also have some of the smallest eggs, which makes sense. The eggs of the Ruby-throated hummingbird are the size of a pea. They are laid in a cup the size of a walnut shell and woven from plant material and spider webs.
One of the unique features of the hummingbird is their wing shape. They can stroke both up and down powerfully and are able to dart forward, backward and straight up and down. They are also the only vertebrates who are able to hover in one place for a sustained amount of time. They can also fly upside down. Hummingbirds also possess extreme stamina and can reach very high speeds. They have been clocked at almost 30 miles per hour during flight and at more than 45 miles per hour in a courtship dive. Those which migrate will often fly more than 18 hours straight, crossing the Gulf of Mexico to their winter grounds.
A hummingbird's heart can reach up to 225 beats per minute at rest and more than 1,200 beats per minute when flying. They beat their wings about 70 times per second when in direct flight and can reach up to 200 times per second when diving.
Hummingbirds are also one of the few bird species which can fall into a torpor, or very deep, sleep-like state. Their metabolic functions will slow down to the very minimum and they maintain a very low body temperature. Hummingbirds can go into torpor during any night of the year, which makes it different from hibernation which is done during a particular season and for a certain length of time. Hummingbirds can fall into torpor whenever food conditions or temperature requires it.
The more than 300 varieties of hummingbirds live exclusively in the New World. They can be found from southern Alaska to Tierra del Fuego. The live anywhere from the high Andes Mountains to steamy tropical jungles, to below sea level and desert plains.
Most hummingbird species live in the tropics, although 17 are regularly found in the United States. These little bundles of energy are fun to watch and certainly among the most beautiful of the bird species.