Hummingbirds, native to the Americas, constitute the biological family Trochilidae, which comprises 355 species across 104 genera. These species are organized into two subfamilies within the family Hummingbirdidae.

Hummingbirds are among the smallest birds, with the smallest, the 5 cm (2.0 in) bee hummingbird, weighing less than 2.0 grams.

They are called hummingbirds because of the buzzing sound created by their wings, which vibrate rapidly like bees" to "whose rapid vibration resembles that of bees. They are also known for their ability to hover in mid-air.

Hummingbirds generally have blue or green plumage with a lighter underbelly, and some males have a crown of feathers or elongated tail feathers. Male hummingbirds are usually blue-green, with some being purple, red or yellow, while females have duller body feathers.

Hummingbirds have a variety of bill morphologies, with the different lengths and shapes of their bills being good indicators of their preferred flowers. Hummingbirds have an extendable, forked tongue that allows them to suck nectar from flowers.

Similar to other birds, hummingbirds have a less developed olfactory system and primarily rely on vision.

Unlike most vertebrates, however, hummingbirds are sensitive to ultraviolet light at 325-360 nm, which helps them find flowers with ultraviolet coloration.

Hummingbirds have the highest basal metabolic rate of any bird or mammal, to conserve energy, especially when food is scarce, they can enter a hibernation-like state at night.

Male hummingbirds of many species establish territories around food sources and guard them to the best of their ability.

Males usually perch in a prominent position to watch for intruders, and if an intruder enters the territory, the male will give a warning and, if necessary, flash iridescent feathers while hovering in mid-air, with the conflict occasionally escalating to a beak-to-beak fight.

Hummingbirds obtain about 90% of their diet from nectar and can also eat a wide variety of insects, including mosquitoes, fruit flies, and lice, in flight or aphids on leaves and spiders' webs.

They obtain amino acids from pollen and insect proteins, and when nectar is scarce, they also draw on sap left over from holes cut by sap-sucking woodpeckers.

The hummingbird's lower bill is flexible and can bend as much as 25 degrees as it widens at the base, creating a larger surface to catch insects. It is also said that hummingbirds have special long, forked tongues that reach into flowers and then use capillary action to suck the nectar out along the tongue.

Hummingbirds are polygamous in their mating habits, with males interacting with females only during the breeding season.

The male does not provide parental nurturing. The female is usually left alone to construct the nest, incubate the eggs, and raise the offspring. Males attract females with song, iridescent plumage, and showy flight.

From an ecological perspective, hummingbirds display specialized traits, like their unique bill shapes, enabling them to adapt to specific environmental conditions.

Specialization, in an evolutionary context, refers to the development of traits that lead to more refined adaptations, influencing species coexistence and the dynamics of ecological communities.