Below a certain temperature hummingbirds can enter a state of torpor. Migratory species and those with more northerly, southerly or mountain distributions tend to fall into torpor more fully during the night. Whether or not a particular bird enters torpor overnight depends not only on the air temperature, but also on how much the bird was able to find to eat around dusk. There are 320 species all of which are found in the Americas from Alaska to Tierra del Fuego. A number of species are migratory and in the colder extremes of their habitat range they are only present during the warmer times of the year.
Hummingbirds have a high requirement for energy because of their very active flight.
They feed on nectar from a variety of flowers and are important pollinators of several groups of plants. Nectar is however low in protein so they also eat a good quantity of insect material. Most Hummingbirds have relatively long bills to aid the acquisition of nectar from flowers. The length of a hummingbirds bill is related to the depth of the corolla of the flowers it feeds from, as many hummingbirds have evolved alongside their preferred food flowers. A bird that only visits one species of flower is far more use as a pollinator to the flower than one who visits many different species and in the process takes its precious pollen to an incompatible flower.