The largest number of hummingbirds are found in the tropics, although they are found in many habitats and are very adaptable. With a name that comes from the noise made in flight by many species, hummingbirds include the smallest of all birds and range in weight from less than 0.07 ounce (2 g) to about 0.7 ounce (20 g). They feed on nectar, although they also consume small insects. They play a significant, and sometimes essential, role in plant reproduction. Strong fliers, they have exceptional flight characteristics for birds, including the ability to hover and fly backwards. Many hummingbirds are known for the brilliance and iridescence of their plumage.