Humming Bird
Hummingbirds are small, nectar-feeding birds native exclusively to the Americas and form the family Trochilidae, comprising about 366 species in 113 genera. Their range extends from southern Alaska to Tierra del Fuego, with the greatest diversity occurring in the tropical and subtropical regions of Central and South America. As of 2024, twenty-one species are classified as endangered or critically endangered, with many others experiencing population decline. Hummingbirds are noted for their extraordinary flight abilities, rapid metabolism, striking plumage—especially in males—and, in some species, long-distance migration.
Among birds, hummingbirds have the widest variety of iridescent colours displayed in blues, greens and purples. Their unique physiological adaptations, including the highest basal metabolic rate of any homeothermic animal, allow them to hover, fly backwards and exhibit exceptional manoeuvrability.
Morphology and Flight
Hummingbirds are the smallest living birds, with adult body lengths typically measured in centimetres. The tiniest species, the bee hummingbird, weighs less than 2 grams, whereas the largest, the giant hummingbird, may weigh up to 20 grams. Their distinctively long, narrow bills vary from straight to strongly curved shapes, enabling efficient extraction of nectar from a wide range of flowers. Although primarily nectarivorous, all species also consume small insects for protein.
Wing morphology is central to their flight capabilities. Long, blade-like wings allow helicopter-like hovering and multidirectional movement. Wing-beat frequencies range from about twelve beats per second in large species to ninety-nine in the little woodstar, one of the fastest recorded. These rapid beats generate the characteristic humming sound used for communication and territorial signalling. Some species use modified tail feathers to produce sounds during courtship displays.
Hummingbirds have short legs and anisodactyl feet with three toes forward and one back. Their claw-like toes have ridged inner surfaces that provide secure grip on flowers and branches. Although they do not walk or hop, they can shuffle sideways while perched. During flight, their feet are tucked tightly against the body to reduce drag. Hummingbirds generate take-off thrust partly through their legs, although less effectively than many other birds.
The metabolic cost of flight demands constant foraging for nectar. To conserve energy, hummingbirds can enter torpor, a nightly state of profound metabolic depression that may reduce their metabolic rate to as low as five per cent of its normal value.
Life Cycle and Behaviour
Most hummingbirds begin breeding at about one year of age. Courtship displays often involve male dives from considerable heights, reaching high speeds to attract females. Mating is brief, lasting only seconds, after which the female alone builds the nest, incubates the eggs and raises the young.
Nests are small cup-shaped structures about five centimetres across, typically attached to slender branches and constructed from spider silk, lichens, moss and plant fibres. Females lay two tiny white eggs—the smallest of any bird species—and incubate them for roughly two to three weeks. The chicks are fed exclusively by the female through regurgitated food and fledge after about three weeks. Lifespans vary, with ruby-throated hummingbirds averaging three to five years, though banding evidence shows individuals living more than nine years. Bee hummingbirds usually live between seven and ten years.
Migration
Although many hummingbird species are sedentary, several undertake migrations. The rufous hummingbird, for example, migrates annually between Alaska and Mexico, travelling thousands of kilometres on a round-trip route—one of the longest migrations relative to body size among birds.
Evolution and Fossil History
Hummingbirds diverged from their closest relatives, the swifts and treeswifts, around forty-two million years ago. The earliest known hummingbird fossil, Eurotrochilus, dates to the Early Oligocene of Europe. Their miniature size, specialised wings and iridescent plumage represent advanced evolutionary adaptations among modern birds.
Habitat and Distribution
Hummingbirds inhabit diverse ecosystems from arid lowlands to high mountain plateaus. The greatest species richness occurs in the humid forests of the northern Andes and adjacent foothills. Some hillstar species live at altitudes exceeding 4,500 metres. Although most species remain in tropical regions year-round, many North American species breed in temperate zones, migrating southwards in winter.
Conservation Status and Population Trends
Reliable population estimates are difficult due to remote habitats, but surveys in North America suggest the following approximate populations:
- Ruby-throated hummingbird: 34 million
- Rufous hummingbird: 19 million
- Black-chinned, Anna’s and broad-tailed hummingbirds: about 8 million each
- Calliope hummingbird: 4 million
- Costa’s and Allen’s hummingbirds: around 2 million each
Some species, however, number only in the hundreds or thousands. According to the IUCN Red List (2024), eight species are critically endangered, thirteen endangered, thirteen vulnerable and twenty near threatened. Two species—the Brace’s emerald and Caribbean emerald—are considered extinct.
In North America, range shifts and population declines have been documented since the 1970s. Rufous, Costa’s, calliope, broad-tailed and Allen’s hummingbirds have declined sharply, some losing more than two-thirds of their numbers since 1970. The ruby-throated hummingbird has declined by about seventeen per cent in the early twenty-first century. Contributing factors include:
- habitat loss and fragmentation,
- collisions with windows,
- predation by domestic cats,
- pesticides reducing insect availability,
- climate-driven disruption of flowering times, migration cues and breeding conditions.
Similar Species
Despite superficial resemblance, hummingbirds are unrelated to sunbirds, an Old World family found in Eurasia, Africa and Australia. Similarities arise from convergent evolution. Certain moths, such as hummingbird hawkmoths in Eurasia, also resemble hummingbirds in flight and feeding behaviour. Species of the genus Hemaris similarly hover while feeding and can be mistaken for hummingbirds at a distance.