Hummingbirds  are native to the  Americas  and are the smallest of birds, most species measuring 3–5  inches in length. The smallest  hummingbird species is the 2.0  inch  Bee Hummingbird, which weighs less than 0.07  oz. The largest hummingbird species is the 9.1   inch Giant Hummingbird, weighing 0.63–0.85  oz.

They are known as hummingbirds because of the humming sound created by their beating  wings, which flap at high frequencies audible to  humans. They hover in mid-air at rapid wing-flapping rates, which vary from around 12 beats per second in the largest species, to in excess of 80 in some of the smallest.

With the exception of  insects, hummingbirds while in flight have the highest  metabolism  of all animals – a necessity to support the rapid beating of their wings during hovering and fast forward flight.  Their  heart rate  can reach as high as 1,260 beats per minute. During flight, oxygen consumption per gram of muscle tissue in a hummingbird is about 10 times higher than that measured in elite human athletes.

Hummingbirds are rare among vertebrates in their ability to rapidly make use of ingested sugars to fuel energetically expensive hovering flight, powering up to 100% of their metabolic needs with the sugars they drink (in comparison, human athletes max out at around 30%). Hummingbirds can use newly-ingested sugars to fuel hovering flight within 30–45 minutes of consumption.

By relying on newly-ingested sugars to fuel flight, hummingbirds can reserve their limited fat stores to sustain their overnight  fasting  or to power migratory flights. Studies of hummingbird metabolism address how a  migrating  Ruby-Throated Hummingbird  can cross 500  miles of the  Gulf of Mexico  on a nonstop flight.  

Probably more than you ever wanted to know about hummingbirds, but we love our little birds who migrate every Spring from Mexico and who stock up on sugar water from our feeder.