Temporal range: Rupelian
from Trinidad and Tobago
Hummingbirds are birds native to the Americas and comprise the biological family Trochilidae. With about 366 species and 113 genera, they occur from Alaska to Tierra del Fuego, but most species are found in Central and South America. About 28 hummingbird species are listed as endangered or critically endangered, with numerous species declining in population.
Hummingbirds have numerous specialized characteristics to enable rapid, maneuverable flight, exceptional metabolic capacity, communication, and long-distance migration in some species. Among all birds, male hummingbirds have the widest diversity of plumage color, particularly in blues, greens, and purples. Hummingbirds are the smallest mature birds, measuring 7.5–13 cm (3–5 in) in length. The smallest is the 5 cm (2.0 in) bee hummingbird, which weighs less than 2.0 g (0.07 oz), and the largest is the 23 cm (9.1 in) giant hummingbird, weighing 18–24 grams (0.63–0.85 oz). Noted for long beaks, hummingbirds are specialized for feeding on flower nectar, but all species also consume small insects.
They are known as hummingbirds because of the humming sound created by their beating wings, which flap at high frequencies audible to other birds and humans. They hover at rapid wing-flapping rates, which vary from around 12 beats per second in the largest species to 80 per second in small hummingbirds.
Hummingbirds have the highest mass-specific metabolic rate of any homeothermic animal. To conserve energy when food is scarce and at night when not foraging, they can enter torpor, a state similar to hibernation, and slow their metabolic rate to 1/15 of its normal rate. While most hummingbirds do not migrate, the rufous hummingbird has one of the longest migrations among birds, traveling twice per year between Alaska and Mexico, a distance of about 3,900 miles (6,300 km).
Hummingbirds split from their sister group, the swifts and treeswifts, around 42 million years ago. The common ancestor of extant hummingbirds is estimated to have lived 22 million years ago in South America.
Hummingbirds are small birds (weighing 2–20 grams (0.071–0.705 oz)) with long, narrow bills. The iridescent colors and highly specialized feathers of many species (mainly in males) give some hummingbirds exotic common names, such as sun gem, fairy, woodstar, sapphire or sylph.
Hummingbirds have a limited distribution in the New World, with more than 300 species in Central and South America, and only about 15 native species, along with 9 vagrant species, in the United States and Canada. The northernmost hummingbird is the rufous (Selasphorus rufus), which breeds as far north as coastal Alaska and throughout British Columbia, while the ruby-throated hummingbird breeds in eastern Canada and eastern United States, migrating to spend winter in the Caribbean region, eastern Mexico, and Central American countries. A total population estimate for the ruby-throated hummingbird is 34 million birds, making it the most populous among hummingbirds in the United States and Canada, while some species are endangered and in decline, with only a few hundred remaining.
Hummingbirds have compact bodies with relatively long, bladelike wings having anatomical structure enabling helicopter-like flight in any direction, including the ability to hover. Particularly while hovering, the wing beats produce the humming sounds, which also may function to alert other birds. In some species, the tail feathers produce sounds used by males during courtship flying. Hummingbirds have extremely rapid wing-beats as high as 80 per second, supported by a high metabolic rate dependent on foraging for sugars from flower nectar. Hummingbirds have low-volume songs that resemble scratches or squeaks. Of those species that have been measured during flying in wind tunnels, the top flight speeds of hummingbird exceed 15 m/s (54 km/h; 34 mph). During courtship, some male species dive from 30 metres (100 ft) of height above a female at speeds around 23 m/s (83 km/h; 51 mph).
The sexes are different in feather coloration, with males having distinct brilliance and ornamentation of head, neck, wing, and breast feathers. The most typical feather ornament in males is the gorget – a bib-like iridescent neck-feather patch that changes brilliance with the viewing angle to attract females and warn male competitors for territory.
Hummingbird females build a nest as a small cup using spider webs, lichens, moss, and loose strings of plant fibers commonly attached to a tree branch. Typically, two pea-shaped white eggs – the smallest of any bird – are incubated over 2-3 weeks in late spring. Fed by regurgitation only from the mother, the chicks fledge in about 3 weeks.
Superficially similar species
Some species of sunbirds – an Old World species restricted in distribution to Eurasia, Africa, and Australia – resemble hummingbirds in appearance and behavior, but are not related to hummingbirds, as their resemblance is due to convergent evolution.
The hummingbird moth has flying and feeding characteristics similar to those of a hummingbird. Hummingbirds may be mistaken for hummingbird hawk-moths, which are large, flying insects with hovering capabilities, and exist only in Eurasia.
Hummingbirds are restricted to the Americas from south central Alaska to Tierra del Fuego, including the Caribbean. The majority of species occur in tropical and subtropical Central and South America, but several species also breed in temperate climates and some hillstars occur even in alpine Andean highlands at altitudes up to 5,200 m (17,100 ft).
The greatest species richness is in humid tropical and subtropical forests of the northern Andes and adjacent foothills, but the number of species found in the Atlantic Forest, Central America or southern Mexico also far exceeds the number found in southern South America, the Caribbean islands, the United States, and Canada. While fewer than 25 different species of hummingbirds have been recorded from the United States and fewer than 10 from Canada and Chile each, Colombia alone has more than 160 and the comparably small Ecuador has about 130 species.
The migratory ruby-throated hummingbird breeds in a range from the Southeastern United States to Ontario, while the black-chinned hummingbird, its close relative and another migrant, is the most widespread and common species in the southwestern United States. The rufous hummingbird is the most widespread species in western North America, and the only hummingbird to be recorded outside of the Americas, having occurred in the Chukchi Peninsula of Russia.
Taxonomy and systematics
The family Trochilidae was introduced in 1825 by Irish zoologist Nicholas Aylward Vigors with Trochilus as the type genus. In traditional taxonomy, hummingbirds are placed in the order Apodiformes, which also contains the swifts, but some taxonomists have separated them into their own order, the Trochiliformes. Hummingbirds' wing bones are hollow and fragile, making fossilization difficult and leaving their evolutionary history poorly documented. Though scientists theorize that hummingbirds originated in South America, where species diversity is greatest, possible ancestors of extant hummingbirds may have lived in parts of Europe and what is southern Russia today.
Around 366 hummingbirds have been identified. They have been traditionally divided into two subfamilies: the hermits (subfamily Phaethornithinae) and the typical hummingbirds (subfamily Trochilinae, all the others). Molecular phylogenetic studies have shown, though, that the hermits are sister to the topazes, making the former definition of the Trochilinae not monophyletic. The hummingbirds form nine major clades: the topazes and jacobins, the hermits, the mangoes, the coquettes, the brilliants, the giant hummingbird (Patagona gigas), the mountaingems, the bees, and the emeralds. The topazes and jacobins combined have the oldest split with the rest of the hummingbirds. The hummingbird family has the third-greatest number of species of any bird family (after the tyrant flycatchers and the tanagers).
Fossil hummingbirds are known from the Pleistocene of Brazil and the Bahamas, but neither has yet been scientifically described, and fossils and subfossils of a few extant species are known. Until recently, older fossils had not been securely identifiable as those of hummingbirds.
In 2004, Gerald Mayr identified two 30-million-year-old hummingbird fossils. The fossils of this primitive hummingbird species, named Eurotrochilus inexpectatus ("unexpected European hummingbird"), had been sitting in a museum drawer in Stuttgart; they had been unearthed in a clay pit at Wiesloch–Frauenweiler, south of Heidelberg, Germany, and, because hummingbirds were assumed to have never occurred outside the Americas, were not recognized to be hummingbirds until Mayr took a closer look at them.
Fossils of birds not clearly assignable to either hummingbirds or a related extinct family, the Jungornithidae, have been found at the Messel pit and in the Caucasus, dating from 35 to 40 million years ago; this indicates that the split between these two lineages indeed occurred around that time. The areas where these early fossils have been found had a climate quite similar to that of the northern Caribbean or southernmost China during that time. The biggest remaining mystery at present is what happened to hummingbirds in the roughly 25 million years between the primitive Eurotrochilus and the modern fossils. The astounding morphological adaptations, the decrease in size, and the dispersal to the Americas and extinction in Eurasia all occurred during this timespan. DNA–DNA hybridization results suggest that the main radiation of South American hummingbirds took place at least partly in the Miocene, some 12 to 13 million years ago, during the uplifting of the northern Andes.
In 2013, a 50-million-year-old bird fossil unearthed in Wyoming was found to be a predecessor to both hummingbirds and swifts before the groups diverged.
Hummingbirds are thought to have split from other members of Apodiformes, the insectivorous swifts (family Apodidae) and treeswifts (family Hemiprocnidae), about 42 million years ago, probably in Eurasia. Despite their current New World distribution, the earliest species of hummingbird occurred in the early Oligocene (Rupelian about 34–28 million years ago) of Europe, belonging to the genus Eurotrochilus, having similar morphology to modern hummingbirds.
A phylogenetic tree unequivocally indicates that modern hummingbirds originated in South America, with the last common ancestor of all living hummingbirds living around 22 million years ago.
A map of the hummingbird family tree – reconstructed from analysis of 284 species – shows rapid diversification from 22 million years ago. Hummingbirds fall into nine main clades – the topazes, hermits, mangoes, brilliants, coquettes, the giant hummingbird, mountaingems, bees, and emeralds – defining their relationship to nectar-bearing flowering plants which attract hummingbirds into new geographic areas.
Molecular phylogenetic studies of the hummingbirds have shown that the family is composed of nine major clades. When Edward Dickinson and James Van Remsen Jr. updated the Howard and Moore Complete Checklist of the Birds of the World for the 4th edition in 2013, they divided the hummingbirds into six subfamilies.
Molecular phylogenetic studies determined the relationships between the major groups of hummingbirds. In the cladogram below, the English names are those introduced in 1997. The Latin names are those introduced in 2013.
While all hummingbirds depend on flower nectar to fuel their high metabolisms and hovering flight, coordinated changes in flower and bill shape stimulated the formation of new species of hummingbirds and plants. Due to this exceptional evolutionary pattern, as many as 140 hummingbird species can coexist in a specific region, such as the Andes range.
The hummingbird evolutionary tree shows one key evolutionary factor appears to have been an altered taste receptor that enabled hummingbirds to seek nectar.
Upon maturity, males of a particular species, Phaethornis longirostris, the long-billed hermit, appear to be evolving a dagger-like weapon on the beak tip as a secondary sexual trait to defend mating areas.
The Andes Mountains appear to be a particularly rich environment for hummingbird evolution because diversification occurred simultaneously with mountain uplift over the past 10 million years. Hummingbirds remain in dynamic diversification inhabiting ecological regions across South America, North America, and the Caribbean, indicating an enlarging evolutionary radiation.
Within the same geographic region, hummingbird clades coevolved with nectar-bearing plant clades, affecting mechanisms of pollination. The same is true for the sword-billed hummingbird (Ensifera ensifera), one of the morphologically most extreme species, and one of its main food plant clades (Passiflora section Tacsonia).
Coevolution with ornithophilous flowers
Hummingbirds are specialized nectarivores tied to the ornithophilous flowers upon which they feed. This coevolution implies that morphological traits of hummingbirds, such as bill length, bill curvature, and body mass are correlated with morphological traits of plants, such as corolla length, curvature, and volume. Some species, especially those with unusual bill shapes, such as the sword-billed hummingbird and the sicklebills, are coevolved with a small number of flower species. Even in the most specialized hummingbird–plant mutualisms, though, the number of food plant lineages of the individual hummingbird species increases with time. The bee hummingbird (Mellisuga helenae) – the world's smallest bird – evolved to dwarfism likely because it had to compete with long-billed hummingbirds having an advantage for nectar foraging from specialized flowers, consequently leading the bee hummingbird to more successfully compete for flower foraging against insects.
Many plants pollinated by hummingbirds produce flowers in shades of red, orange, and bright pink, though the birds take nectar from flowers of other colors as well. Hummingbirds can see wavelengths into the near-ultraviolet, but hummingbird-pollinated flowers do not reflect these wavelengths as many insect-pollinated flowers do. This narrow color spectrum may render hummingbird-pollinated flowers relatively inconspicuous to most insects, thereby reducing nectar robbing. Hummingbird-pollinated flowers also produce relatively weak nectar (averaging 25% sugars w/w) containing a high proportion of sucrose, whereas insect-pollinated flowers typically produce more concentrated nectars dominated by fructose and glucose.
Hummingbirds and the plants they visit for nectar have a tight coevolutionary association, generally called a plant–bird mutualistic network. These birds show high specialization and modularity, especially in communities with high species richness. These associations are also observed when closely related hummingbirds, for example two species of the same genus, visit distinct sets of flowering species.
Hummingbirds exhibit sexual size dimorphism according to Rensch's rule, in which males are smaller than females in small-bodied species, and males are larger than females in large-bodied species. The extent of this sexual size difference varies among clades of hummingbirds. For example, the Mellisugini clade (bees) exhibits a large size dimorphism, with females being larger than males. Conversely, the Lesbiini clade (coquettes) displays very little size dimorphism; males and females are similar in size. Sexual dimorphisms in bill size and shape are also present between male and female hummingbirds, where in many clades, females have longer, more curved bills favored for accessing nectar from tall flowers. For males and females of the same size, females tend to have larger bills.
Sexual size and bill differences likely evolved due to constraints imposed by courtship, because mating displays of male hummingbirds require complex aerial maneuvers. Males tend to be smaller than females, allowing conservation of energy to forage competitively and participate more frequently in courtship. Thus, sexual selection favors smaller male hummingbirds.
Female hummingbirds tend to be larger, requiring more energy, with longer beaks that allow for more effective reach into crevices of tall flowers for nectar. Thus, females are better at foraging, acquiring flower nectar, and supporting the energy demands of their larger body size. Directional selection thus favors the larger hummingbirds in terms of acquiring food.
Another evolutionary cause of this sexual bill dimorphism is that the selective forces from competition for nectar between the sexes of each species drives sexual dimorphism. Depending on which sex holds territory in the species, the other sex having a longer bill and being able to feed on a wide variety of flowers is advantageous, decreasing intraspecific competition. For example, in species of hummingbirds where males have longer bills, males do not hold a specific territory and have a lek mating system. In species where males have shorter bills than females, males defend their resources, so females benefit from a longer bill to feed from a broader range of flowers.
The hummingbird plumage coloration gamut, particularly for blue, green, and purple colors in the gorget and crown of males, occupies 34% of the total color space for bird feathers. White (unpigmented) feathers have the lowest incidence in the hummingbird color gamut. Hummingbird plumage color diversity evolved from sexual and social selection on plumage coloration, which correlates with the rate of hummingbird species development over millions of years. Bright plumage colors in males are part of aggressive competition for flower resources and mating. The bright colors result both from pigmentation in the feathers and from prismal cells within the top layers of feathers of the head, gorget, breast, back and wings. When sunlight hits these cells, it is split into wavelengths that reflect to the observer in varying degrees of intensity, with the feather structure acting as a diffraction grating. Iridescent hummingbird colors result from a combination of refraction and pigmentation, since the diffraction structures themselves are made of melanin, a pigment, and may also be colored by carotenoid pigmentation and more subdued black, brown or gray colors dependent on melanin.
By merely shifting position, feather regions of a muted-looking bird can instantly become fiery red or vivid green. In courtship displays for one example, males of the colorful Anna's hummingbird orient their bodies and feathers toward the sun to enhance the display value of iridescent plumage toward a female of interest.
One study of Anna's hummingbirds found that dietary protein was an influential factor in feather color, as birds receiving more protein grew significantly more colorful crown feathers than those fed a low-protein diet. Additionally, birds on a high-protein diet grew yellower (higher hue) green tail feathers than birds on a low-protein diet.
Specialized characteristics and metabolism
Hummingbirds are named for the prominent humming sound their wingbeats make while flying and hovering to feed or interact with other hummingbirds. Humming serves communication purposes by alerting other birds of the arrival of a fellow forager or potential mate. The humming sound derives from aerodynamic forces generated by both the downstrokes and upstrokes of the rapid wingbeats, causing oscillations and harmonics that evoke an acoustic quality likened to that of a musical instrument. The humming sound of hummingbirds is unique among flying animals, compared to the whine of mosquitoes, buzz of bees, and "whoosh" of larger birds.
The wingbeats causing the hum of hummingbirds during hovering are achieved by elastic recoil of wing strokes produced by the main flight muscles: the pectoralis major (the main downstroke muscle) and supracoracoideus (the main upstroke muscle).
Although hummingbird eyes are small in diameter (5–6 mm), they are accommodated in the skull by reduced skull ossification, and occupy a larger proportion of the skull compared to other birds and animals. Further, hummingbird eyes have large corneas, which comprise about 50% of the total transverse eye diameter, combined with an extraordinary density of retinal ganglion cells responsible for visual processing, containing some 45,000 neurons per mm2. The enlarged cornea relative to total eye diameter serves to increase the amount of light perception by the eye when the pupil is dilated maximally, enabling nocturnal flight.
During evolution, hummingbirds adapted to the navigational needs of visual processing while in rapid flight or hovering by development of the exceptionally dense array of retinal neurons, allowing for increased spatial resolution in the lateral and frontal visual fields. Morphological studies of the hummingbird brain showed that neuronal hypertrophy – relatively the largest in any bird – exists in a region called the pretectal nucleus lentiformis mesencephali (called the nucleus of the optic tract in mammals) responsible for refining dynamic visual processing while hovering and during rapid flight.
The enlargement of the brain region responsible for visual processing indicates an enhanced ability for perception and processing of fast-moving visual stimuli encountered during rapid forward flight, insect foraging, competitive interactions, and high-speed courtship. A study of broad-tailed hummingbirds indicated that hummingbirds have a fourth color-sensitive visual cone (humans have three) that detects ultraviolet light and enables discrimination of non-spectral colors, possibly having a role in flower identity, courtship displays, territorial defense, and predator evasion. The fourth color cone would extend the range of visible colors for hummingbirds to perceive ultraviolet light and color combinations of feathers and gorgets, colorful plants, and other objects in their environment, enabling detection of as many as five non-spectral colors, including purple, ultraviolet-red, ultraviolet-green, ultraviolet-yellow, and ultraviolet-purple.
Hummingbirds are highly sensitive to stimuli in their visual fields, responding to even minimal motion in any direction by reorienting themselves in midflight. Their visual sensitivity allows them to precisely hover in place while in complex and dynamic natural environments, functions enabled by the lentiform nucleus which is tuned to fast-pattern velocities, enabling highly-tuned control and collision avoidance during forward flight.
With the exception of insects, hummingbirds have the highest metabolism of all animals – a necessity to support the rapid beating of their wings during hovering and fast forward flight. During flight and hovering, oxygen consumption per gram of muscle tissue in a hummingbird is about 10 times higher than that measured in elite human athletes. Hummingbirds achieve this extraordinary capacity for oxygen consumption by an exceptional density and proximity of capillaries and mitochondria in their flight muscles.
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 maximize around 30%). Hummingbirds can use newly ingested sugars to fuel hovering flight within 30–45 minutes of consumption. These data suggest that hummingbirds are able to oxidize sugar in flight muscles at rates rapid enough to satisfy their extreme metabolic demands – as indicated by a 2017 review showing that hummingbirds have in their flight muscles a mechanism for "direct oxidation" of sugars into maximal ATP yield to support a high metabolic rate for hovering, foraging at altitude, and migrating. This adaptation occurred through the evolutionary loss of a key gene, fructose-bisphosphatase 2 (FBP2), coinciding with the onset of hovering by hummingbirds estimated by fossil evidence to be some 35 million years ago. Without FBP2, glycolysis and mitochondrial respiration in flight muscles are enhanced, enabling hummingbirds to metabolize sugar more efficiently for energy.
By relying on newly ingested sugars to fuel flight, hummingbirds 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 800 km (500 mi) of the Gulf of Mexico on a nonstop flight. This hummingbird, like other long-distance migrating birds, stores fat as a fuel reserve augmenting its weight by as much as 100%, then enabling metabolic fuel for flying over open water.
The heart rate of hummingbirds can reach as high as 1,260 beats per minute, a rate measured in a blue-throated hummingbird with a breathing rate of 250 breaths per minute at rest.
Hemoglobin adaptation to altitude
Dozens of hummingbird species live year-round in tropical mountain habitats at high altitudes, such as in the Andes over ranges of 1,500 metres (4,900 ft) to 5,200 metres (17,100 ft) where the partial pressure of oxygen in the air is reduced, a condition of hypoxic challenge for the high metabolic demands of hummingbirds. In Andean hummingbirds living at high elevations, researchers found that the oxygen-carrying protein in blood – hemoglobin – had increased oxygen-binding affinity, and that this adaptive effect likely resulted from evolutionary mutations within the hemoglobin molecule via specific amino acid changes due to natural selection.
The high metabolic rate of hummingbirds – especially during rapid forward flight and hovering – produces increased body heat that requires specialized mechanisms of thermoregulation for heat dissipation, which becomes an even greater challenge in hot, humid climates. Hummingbirds dissipate heat partially by evaporation through exhaled air, and from body structures with thin or no feather covering, such as around the eyes, shoulders, under the wings (patagia), and feet.
While hovering, hummingbirds do not benefit from the heat loss by air convection during forward flight, except for air movement generated by their rapid wing-beat, possibly aiding convective heat loss from the extended feet. Smaller hummingbird species, such as the calliope, appear to adapt their relatively higher surface-to-volume ratio to improve convective cooling from air movement by the wings. When air temperatures rise above 36 °C (97 °F), thermal gradients driving heat passively by convective dissipation from around the eyes, shoulders, and feet are reduced or eliminated, requiring heat dissipation mainly by evaporation and exhalation. In cold climates, hummingbirds retract their feet into breast feathers to eliminate skin exposure and minimize heat dissipation.
The dynamic range of metabolic rates in hummingbirds requires a parallel dynamic range in kidney function. During a day of nectar consumption with a corresponding high water intake that may total five times the body weight per day, hummingbird kidneys process water via glomerular filtration rates (GFR) in amounts proportional to water consumption, thereby avoiding overhydration. During brief periods of water deprivation, however, such as in nighttime torpor, GFR drops to zero, preserving body water.
Hummingbird kidneys also have a unique ability to control the levels of electrolytes after consuming nectars with high amounts of sodium and chloride or none, indicating that kidney and glomerular structures must be highly specialized for variations in nectar mineral quality. Morphological studies on Anna's hummingbird kidneys showed adaptations of high capillary density in close proximity to nephrons, allowing for precise regulation of water and electrolytes.
Song, vocal learning, and hearing
Many hummingbird species exhibit a diverse vocal repertoire of chirps, squeaks, whistles and buzzes. Vocalizations vary in complexity and spectral content during social interactions, foraging, territorial defense, courtship, and mother-nestling communication. Territorial vocal signals may be produced in rapid succession to discourage aggressive encounters, with the chirping rate and loudness increasing when intruders persist. During the breeding season, both male and female hummingbirds vocalize as part of courtship.
Hummingbirds exhibit vocal production learning to enable song variation – "dialects" that exist across the same species. For example, the blue-throated hummingbird's song differs from typical oscine songs in its wide frequency range, extending from 1.8 kHz to about 30 kHz. It also produces ultrasonic vocalizations which do not function in communication. As blue-throated hummingbirds often alternate singing with catching small flying insects, it is possible the ultrasonic clicks produced during singing disrupt insect flight patterns, making insects more vulnerable to predation. Anna's, Costa's, long-billed hermits, and Andean hummingbirds have song dialects that vary across habitat locations and phylogenetic clades.
The avian vocal organ, the syrinx, plays an important role in understanding hummingbird song production. What makes the hummingbird's syrinx different from that of other birds in the Apodiformes order is the presence of internal muscle structure, accessory cartilages, and a large tympanum that serves as an attachment point for external muscles, all of which are adaptations thought to be responsible for the hummingbird's increased ability in pitch control and large frequency range.
Hummingbird songs originate from at least seven specialized nuclei in the forebrain. A genetic expression study showed that these nuclei enable vocal learning (ability to acquire vocalizations through imitation), a rare trait known to occur in only two other groups of birds (parrots and songbirds) and a few groups of mammals (including humans, whales and dolphins, and bats). Within the past 66 million years, only hummingbirds, parrots, and songbirds out of 23 bird orders may have independently evolved seven similar forebrain structures for singing and vocal learning, indicating that evolution of these structures is under strong epigenetic constraints possibly derived from a common ancestor.
Generally, birds have been assessed to vocalize and hear in the range of 2–5 kHz, with hearing sensitivity falling with higher frequencies. In the Ecuadorian hillstar (Oreotrochilus chimborazo), vocalizations were recorded in the wild to be at a frequency above 10 Hz, well outside of the known hearing ability of most birds. Song system nuclei in the hummingbird brain are similar to those songbird brains, but the hummingbird brain has specialized regions involved for song processing.
The metabolism of hummingbirds can slow at night or at any time when food is not readily available; the birds enter a deep-sleep state (known as torpor) to prevent energy reserves from falling to a critical level. One study of broad-tailed hummingbirds found that body weight decreased linearly throughout torpor at a rate of 0.04 g per hour.
During nighttime torpor, body temperature in a Caribbean hummingbird was shown to fall from 40 to 18 °C, with heart and breathing rates both slowed dramatically (heart rate of roughly 50 to 180 bpm from its daytime rate of higher than 1000 bpm). Recordings from a Metallura phoebe hummingbird in noctural torpor at around 3,800 metres (12,500 ft) in the Andes mountains showed that body temperature fell to 3.3 °C (38 °F), the lowest known level for a bird or non-hibernating mammal. During cold nights at altitude, hummingbirds were in torpor for 2-13 hours depending on species, with cooling occurring at the rate of 0.6 °C per minute and rewarming at 1-1.5 °C per minute. High-altitude Andean hummingbirds also lost body weight in negative proportion to how long the birds were in torpor, losing about 6% of weight each night.
During torpor, to prevent dehydration, the kidney function declines, preserving needed compounds, such as glucose, water, and nutrients. The circulating hormone, corticosterone, is one signal that arouses a hummingbird from torpor.
Use and duration of torpor vary among hummingbird species and are affected by whether a dominant bird defends territory, with nonterritorial subordinate birds having longer periods of torpor. A hummingbird with a higher fat percentage will be less likely to enter a state of torpor compared to one with less fat, as a bird can use the energy from its fat stores. Torpor in hummingbirds appears to be unrelated to nighttime temperature, as it occurs across a wide temperature range, with energy savings of such deep sleep being more related to the photoperiod and duration of torpor.
Hummingbirds have unusually long lifespans for organisms with such rapid metabolisms. Though many die during their first year of life, especially in the vulnerable period between hatching and fledging, those that survive may occasionally live a decade or more. Among the better-known North American species, the typical lifespan is probably 3 to 5 years. For comparison, the smaller shrews, among the smallest of all mammals, seldom live longer than 2 years. The longest recorded lifespan in the wild relates to a female broad-tailed hummingbird that was banded (ringed) as an adult at least one year old, then recaptured 11 years later, making her at least 12 years old. Other longevity records for banded hummingbirds include an estimated minimum age of 10 years 1 month for a female black-chinned hummingbird similar in size to the broad-tailed hummingbird, and at least 11 years 2 months for a much larger buff-bellied hummingbird.
Praying mantises have been observed as predators of hummingbirds. Other predators include dragonflies, frogs, orb-weaver spiders, and other birds, such as the roadrunner.
Male hummingbirds do not take part in nesting. Most species build a cup-shaped nest on the branch of a tree or shrub. The nest varies in size relative to the particular species – from smaller than half a walnut shell to several centimeters in diameter.
Many hummingbird species use spider silk and lichen to bind the nest material together and secure the structure. The unique properties of the silk allow the nest to expand as the young hummingbirds grow. Two white eggs are laid, which despite being the smallest of all bird eggs, are large relative to the adult hummingbird's size. Incubation lasts 14 to 23 days, depending on the species, ambient temperature, and female attentiveness to the nest. The mother feeds her nestlings on small arthropods and nectar by inserting her bill into the open mouth of a nestling, and then regurgitating the food into its crop. Hummingbirds stay in the nest for 18–22 days, after which they leave the nest to forage on their own, although the mother bird may continue feeding them for another 25 days.
Hummingbird flight has been studied intensively from an aerodynamic perspective using wind tunnels and high-speed video cameras. Two studies of rufous or Anna's hummingbirds in a wind tunnel used particle image velocimetry techniques to investigate the lift generated on the bird's upstroke and downstroke. The birds produced 75% of their weight support during the downstroke and 25% during the upstroke, with the wings making a "figure 8" motion.
Many earlier studies had assumed that lift was generated equally during the two phases of the wingbeat cycle, as is the case of insects of a similar size. This finding shows that hummingbird hovering is similar to, but distinct from, that of hovering insects such as the hawk moth. Further studies using electromyography in hovering rufous hummingbirds showed that muscle strain in the pectoralis major (principal downstroke muscle) was the lowest yet recorded in a flying bird, and the primary upstroke muscle (supracoracoideus) is proportionately larger than in other bird species. Presumably due to rapid wingbeats for flight and hovering, hummingbird wings have adapted to perform without an alula.
The giant hummingbird's wings beat as few as 12 per second, and the wings of typical hummingbirds beat up to 80 times per second. As air density decreases, for example, at higher altitudes, the amount of power a hummingbird must use to hover increases. Hummingbird species adapted for life at higher altitudes, therefore, have larger wings to help offset these negative effects of low air density on lift generation.
A slow-motion video has shown how the hummingbirds deal with rain when they are flying. To remove the water from their heads, they shake their heads and bodies, similar to a dog shaking, to shed water. Further, when raindrops collectively may weigh as much as 38% of the bird's body weight, hummingbirds shift their bodies and tails horizontally, beat their wings faster, and reduce their wings' angle of motion when flying in heavy rain.
Wingbeats and flight stability
The highest recorded wingbeats for wild hummingbirds during hovering is 88 per second, as measured for the purple-throated woodstar (Calliphlox mitchellii) weighing 3.2 g. The number of beats per second increases above "normal" while hovering during courtship displays (up to 90 per second for the calliope hummingbird, Selasphorus calliope), a wingbeat rate 40% higher than its typical hovering rate.
During turbulent airflow conditions created experimentally in a wind tunnel, hummingbirds exhibit stable head positions and orientation when they hover at a feeder. When wind gusts from the side, hummingbirds compensate by increasing wing-stroke amplitude and stroke plane angle and by varying these parameters asymmetrically between the wings and from one stroke to the next. They also vary the orientation and enlarge the collective surface area of their tail feathers into the shape of a fan. While hovering, the visual system of a hummingbird is able to separate apparent motion caused by the movement of the hummingbird itself from motions caused by external sources, such as an approaching predator. In natural settings full of highly complex background motion, hummingbirds are able to precisely hover in place by rapid coordination of vision with body position.
When courting, the male Anna's hummingbird ascends some 35 m (115 ft) above a female, before diving at a speed of 27 m/s (89 ft/s), equal to 385 body lengths/sec – producing a high-pitched sound near the female at the nadir of the dive. This downward acceleration during a dive is the highest reported for any vertebrate undergoing a voluntary aerial maneuver; in addition to acceleration, the speed relative to body length is the highest known for any vertebrate. For instance, it is about twice the diving speed of peregrine falcons in pursuit of prey. At maximum descent speed, about 10 g of gravitational force occur in the courting hummingbird during a dive (Note: G-force is generated as the bird pulls out of the dive).[a]
The outer tail feathers of male Anna's (Calypte anna) and Selasphorus hummingbirds (e.g., Allen's, calliope) vibrate during courtship display dives and produce an audible chirp caused by aeroelastic flutter. Hummingbirds cannot make the courtship dive sound when missing their outer tail feathers, and those same feathers could produce the dive sound in a wind tunnel. The bird can sing at the same frequency as the tail-feather chirp, but its small syrinx is not capable of the same volume. The sound is caused by the aerodynamics of rapid air flow past tail feathers, causing them to flutter in a vibration, which produces the high-pitched sound of a courtship dive.
Many other species of hummingbirds also produce sounds with their wings or tails while flying, hovering, or diving, including the wings of the calliope hummingbird, broad-tailed hummingbird, rufous hummingbird, Allen's hummingbird, and the streamertail species, as well as the tail of the Costa's hummingbird and the black-chinned hummingbird, and a number of related species. The harmonics of sounds during courtship dives vary across species of hummingbirds.
Wing feather trill
Male rufous and broad-tailed hummingbirds (genus Selasphorus) have a distinctive wing feature during normal flight that sounds like jingling or a buzzing shrill whistle – a trill. The trill arises from air rushing through slots created by the tapered tips of the ninth and tenth primary wing feathers, creating a sound loud enough to be detected by female or competitive male hummingbirds and researchers up to 100 m away.
Behaviorally, the trill serves several purposes: It announces the sex and presence of a male bird; it provides audible aggressive defense of a feeding territory and an intrusion tactic; it enhances communication of a threat; and it favors mate attraction and courtship.
Relatively few hummingbirds migrate as a percentage of the total number of species; of the roughly 366 known hummingbird species, only 12–15 species migrate annually, particularly those in North America. Most hummingbirds live in the Amazonia-Central America tropical rainforest belt, where seasonal temperature changes and food sources are relatively constant, obviating the need to migrate. As the smallest living birds, hummingbirds are relatively limited at conserving heat energy, and are generally unable to maintain a presence in higher latitudes during winter months, unless the specific location has a large food supply throughout the year, particularly access to flower nectar. Other migration factors are seasonal fluctuation of food, climate, competition for resources, predators, and inherent signals.
Most North American hummingbirds migrate southward in fall to spend winter in Mexico, the Caribbean Islands, or Central America. A few southern South American species also move north to the tropics during the southern winter. A few species are year-round residents of Florida, California, and the far southwestern desert regions of the US. Among these are Anna's hummingbird, a common resident from southern Arizona and inland California, and the buff-bellied hummingbird, a winter resident from Florida across the Gulf Coast to South Texas. Ruby-throated hummingbirds are common along the Atlantic flyway, and migrate in summer from as far north as Atlantic Canada, returning to Mexico, South America, southern Texas, and Florida to winter. During winter in southern Louisiana, black-chinned, buff-bellied, calliope, Allen's, Anna's, ruby-throated, rufous, broad-tailed, and broad-billed hummingbirds are present.
The rufous hummingbird breeds farther north than any other species of hummingbird, often breeding in large numbers in temperate North America and wintering in increasing numbers along the coasts of the subtropical Gulf of Mexico and Florida, rather than in western or central Mexico. By migrating in spring as far north as the Yukon or southern Alaska, the rufous hummingbird migrates more extensively and nests farther north than any other hummingbird species, and must tolerate occasional temperatures below freezing in its breeding territory. This cold hardiness enables it to survive temperatures below freezing, provided that adequate shelter and food are available.
As calculated by displacement of body size, the rufous hummingbird makes perhaps the longest migratory journey of any bird in the world. At just over 3 inches (7.6 cm) long, rufous hummingbirds travel 3,900 miles (6,300 km) one-way from Alaska to Mexico in late summer, a distance equal to 78,470,000 body lengths, then make the return journey in the following spring. By comparison, the 13 inches (33 cm)-long Arctic tern makes a one-way flight of about 11,185 miles (18,001 km), or 51,430,000 body lengths, just 65% of the body displacement during migration by rufous hummingbirds.
The northward migration of rufous hummingbirds occurs along the Pacific flyway and may be time-coordinated with flower and tree-leaf emergence in spring in early March, and also with availability of insects as food. Arrival at breeding grounds before nectar availability from mature flowers may jeopardize breeding opportunities.
For nutrition, hummingbirds eat a variety of insects, including mosquitoes, fruit flies, gnats in flight, or aphids on leaves and spiders in their webs. The lower beak of hummingbirds is flexible and can bend as much as 25 degrees when it widens at the base, making a larger surface for catching insects. Hummingbirds hover within insect swarms in a method called "hover-hawking" to facilitate feeding.
To supply energy needs, hummingbirds drink nectar, a sweet liquid inside certain flowers. Like bees, they are able to assess the amount of sugar in the nectar they drink; they normally reject flower types that produce nectar that is less than 10% sugar and prefer those whose sugar content is higher. Nectar is a mixture of glucose, fructose, and sucrose, and is a poor source of other nutrients, requiring hummingbirds to meet their nutritional needs by consuming insects.
Hummingbirds do not spend all day flying, as the energy cost would be prohibitive; the majority of their activity consists simply of sitting or perching. Hummingbirds eat many small meals and consume around half their weight in nectar (twice their weight in nectar, if the nectar is 25% sugar) each day. Hummingbirds digest their food rapidly due to their small size and high metabolism; a mean retention time less than an hour has been reported. Hummingbirds spend an average of 20% of their time feeding and 75–80% sitting and digesting.
Because their high metabolism makes them vulnerable to starvation, hummingbirds are highly attuned to food sources. Some species, including many found in North America, are territorial and try to guard food sources (such as a feeder) against other hummingbirds, attempting to ensure a future food supply. Additionally, hummingbirds have an enlarged hippocampus, a brain region facilitating spatial memory used to map flowers previously visited during nectar foraging.
Hummingbird beaks are flexible and their shapes vary dramatically as an adaptation for specialized feeding. Some species, such as hermits (Phaethornis spp.) have long bills that allow them to probe deep into flowers with long corollae. Thornbills have short, sharp bills adapted for feeding from flowers with short corollae and piercing the bases of longer ones. The sicklebills' extremely decurved bills are adapted to extracting nectar from the curved corollae of flowers in the family Gesneriaceae. The bill of the fiery-tailed awlbill has an upturned tip adapted for feeding on nectar from tubular flowers while hovering. Hummingbird bill sizes range from about 5 mm to as long as 100 mm (about 4 in). When catching insects in flight, a hummingbird's jaw flexes downward to widen the beak for successful capture.
Perception of sweet nectar
Perception of sweetness in nectar evolved in hummingbirds during their genetic divergence from insectivorous swifts, their closest bird relatives. Although the only known sweet sensory receptor, called T1R2, is absent in birds, receptor expression studies showed that hummingbirds adapted a carbohydrate receptor from the T1R1-T1R3 receptor, identical to the one perceived as umami in humans, essentially repurposing it to function as a nectar sweetness receptor. This adaptation for taste enabled hummingbirds to detect and exploit sweet nectar as an energy source, facilitating their distribution across geographical regions where nectar-bearing flowers are available.
Tongue as a micropump
Hummingbirds drink with their long tongues by rapidly lapping nectar. Their tongues have semicircular tubes which run down their lengths to facilitate nectar consumption via rapid pumping in and out of the nectar. While capillary action was believed to be what drew nectar into these tubes, high-speed photography revealed that the tubes open down their sides as the tongue goes into the nectar, and then close around the nectar, trapping it so it can be pulled back into the beak over a period of 14 milliseconds per lick at a rate of up to 20 licks per second. The tongue, which is forked, is compressed until it reaches nectar, then the tongue springs open, the rapid action traps the nectar which moves up the grooves, like a pump action, with capillary action not involved. Consequently, tongue flexibility enables accessing, transporting and unloading nectar via pump action, not by a capillary syphon as once believed.
Feeders and artificial nectar
In the wild, hummingbirds visit flowers for food, extracting nectar, which is 55% sucrose, 24% glucose, and 21% fructose on a dry-matter basis. Hummingbirds also take sugar-water from bird feeders, which allow people to observe and enjoy hummingbirds up close while providing the birds with a reliable source of energy, especially when flower blossoms are less abundant. A negative aspect of artificial feeders, however, is that the birds may seek less flower nectar for food, and so may reduce the amount of pollination their feeding naturally provides.
White granulated sugar is used in hummingbird feeders in a 20% concentration as a common recipe, although hummingbirds will defend feeders more aggressively when sugar content is at 35%, indicating preference for nectar with higher sugar content. Organic and "raw" sugars contain iron, which can be harmful, and brown sugar, agave syrup, molasses, and artificial sweeteners also should not be used. Honey is made by bees from the nectar of flowers, but it is not good to use in feeders because when it is diluted with water, microorganisms easily grow in it, causing it to spoil rapidly.
Red food dye was once thought to be a favorable ingredient for the nectar in home feeders, but it is unnecessary. Commercial products sold as "instant nectar" or "hummingbird food" may also contain preservatives or artificial flavors, as well as dyes, which are unnecessary and potentially harmful. Although some commercial products contain small amounts of nutritional additives, hummingbirds obtain all necessary nutrients from the insects they eat, rendering added nutrients unnecessary.
Visual cues of foraging
Hummingbirds have exceptional visual acuity providing them with discrimination of food sources while foraging. Although hummingbirds are thought to be attracted to color while seeking food, such as red flowers or artificial feeders, experiments indicate that location and flower nectar quality are the most important "beacons" for foraging. Hummingbirds depend little on visual cues of flower color to beacon to nectar-rich locations, but rather they use surrounding landmarks to find the nectar reward.
In at least one hummingbird species – the green-backed firecrown (Sephanoides sephaniodes) – flower colors preferred are in the red-green wavelength for the bird's visual system, providing a higher contrast than for other flower colors. Further, the crown plumage of firecrown males is highly iridescent in the red wavelength range (peak at 650 nanometers), possibly providing a competitive advantage of dominance when foraging among other hummingbird species with less colorful plumage. The ability to discriminate colors of flowers and plumage is enabled by a visual system having four single cone cells and a double cone screened by photoreceptor oil droplets which enhance color discrimination.
While hummingbirds rely primarily on vision and hearing to assess competition from bird and insect foragers near food sources, they may also be able to detect by smell the presence in nectar of insect defensive chemicals (such as formic acid) and aggregation pheromones of foraging ants, which discourage feeding.
In myth and culture
Aztecs wore hummingbird talismans, both artistic representations of hummingbirds and fetishes made from actual hummingbird parts as emblematic for vigor, energy, and propensity to do work along with their sharp beaks that symbolically mimic instruments of weaponry, bloodletting, penetration, and intimacy. Hummingbird talismans were prized as drawing sexual potency, energy, vigor, and skill at arms and warfare to the wearer. The Aztec god of war Huitzilopochtli is often depicted in art as a hummingbird. Aztecs believed that fallen warriors would be reincarnated as hummingbirds. The Nahuatl word huitzil translates to hummingbird. One of the Nazca Lines depicts a hummingbird (right).
Trinidad and Tobago, known as "The land of the hummingbird," displays a hummingbird on that nation's coat of arms, 1-cent coin, and livery on its national airline, Caribbean Airlines.
Mt. Umunhum in the Santa Cruz Mountains of Northern California is Ohlone for "resting place of the hummingbird". The Hopi and Zuni cultures have a hummingbird creation myth about a young brother and sister who are starving because drought and famine have come to the land. Their parents have left to find food, so the boy carves a piece of wood into a small bird to entertain his sister. When the girl tosses the carving into the air, the bird comes to life, turning into a hummingbird. The small bird then flies to the God of Fertility and begs for rain, and the god obliges the request, which helps the crops to grow again.
The Gibson Hummingbird is an acoustic guitar model described as having the shape of a hummingbird by Gibson Brands, a major guitar manufacturer. During the costume competition of the Miss Universe 2016 beauty pageant, Miss Ecuador, Connie Jiménez, wore a costume inspired by hummingbird wing feathers.
A color plate illustration from Ernst Haeckel's Kunstformen der Natur (1899), showing a variety of hummingbirds
Fallen Anna's hummingbird nest shown next to a toothpick for scale
- AeroVironment Nano Hummingbird – artificial hummingbird
- ^ By comparison to humans, this is a G-force acceleration well beyond the threshold of causing near loss of consciousness (occurring at about +5 Gz) in fighter pilots during operation of a fixed-wing aircraft in a high-speed banked turn.
- ^ Gill, F.; Donsker, D.; Rasmussen, P. (29 January 2023). "IOC World Bird List (v 13.1), International Ornithological Committee". IOC World Bird List. doi:10.14344/IOC.ML.11.2. Retrieved 5 March 2023.
- ^ a b c d e f Stonich, Kathryn (26 April 2021). "Hummingbirds of the United States: A Photo List of All Species". American Bird Conservancy. Retrieved 7 March 2023.
- ^ English, Simon G.; Bishop, Christine A.; Wilson, Scott; Smith, Adam C. (15 September 2021). "Current contrasting population trends among North American hummingbirds". Scientific Reports. 11 (1). doi:10.1038/s41598-021-97889-x. ISSN 2045-2322.
- ^ a b c d e f g Venable, G.X.; Gahm, K.; Prum, R.O. (June 2022). "Hummingbird plumage color diversity exceeds the known gamut of all other birds". Communications Biology. 5 (1): 576. doi:10.1038/s42003-022-03518-2. PMC 9226176. PMID 35739263.
- ^ a b c Suarez, R.K. (1992). "Hummingbird flight: Sustaining the highest mass-specific metabolic rates among vertebrates". Experientia. 48 (6): 565–570. doi:10.1007/bf01920240. PMID 1612136. S2CID 21328995.
- ^ "Hummingbirds". Nationalzoo.si.edu. Archived from the original on 16 July 2012. Retrieved 1 April 2013.
- ^ a b c d e f g h i j "What is a hummingbird?". Smithsonian’s National Zoo and Conservation Biology Institute. 2023. Retrieved 7 March 2023.
- ^ a b c d e f g h i j k "Hummingbird". Encyclopaedia Britannica. 2023. Retrieved 7 March 2023.
- ^ Clark, C.J.; Dudley, R. (2009). "Flight costs of long, sexually selected tails in hummingbirds". Proceedings of the Royal Society B: Biological Sciences. 276 (1664): 2109–115. doi:10.1098/rspb.2009.0090. PMC 2677254. PMID 19324747.
- ^ Ridgely, R.S.; Greenfield, P.G. (2001). The Birds of Ecuador, Field Guide (1 ed.). Cornell University Press. ISBN 978-0-8014-8721-7.
- ^ a b White, Richard (19 September 2015). "Hummingbird hawk moth, hummingbird and sunbird". Bird Ecology Study Group. Retrieved 8 March 2023.
- ^ Prinzinger, R.; Schafer, T.; Schuchmann, K.L. (1992). "Energy metabolism, respiratory quotient and breathing parameters in two convergent small bird species : the fork-tailed sunbird Aethopyga christinae (Nectariniidae) and the chilean hummingbird Sephanoides sephanoides (Trochilidae)". Journal of Thermal Biology. 17 (2): 71–79. doi:10.1016/0306-4565(92)90001-V.
- ^ Moisset, Beatriz (2022). "Hummingbird moth (Hemaris spp.)". Forest Service, US Department of Agriculture. Retrieved 2 August 2022.
- ^ Fjeldså, J.; Heynen, I. (1999). Genus Oreotrochilus. In: del Hoyo, J., A. Elliott, & J. Sargatal. eds. (1999). Handbook of the Birds of the World. Vol. 5. Barn-owls to Hummingbirds. Lynx Edicions, Barcelona. pp. 623–624. ISBN 84-87334-25-3.
- ^ Jaramillo, A. & R. Barros (2010). Species lists of birds for South American countries and territories: Chile.
- ^ Salaman, P., T. Donegan, & D. Caro (2009). Checklist to the Birds of Colombia 2009. Archived 2009-08-24 at the Wayback Machine Conservation Colombiana 8. Fundación ProAves
- ^ Freile, J. (2009). Species lists of birds for South American countries and territories: Ecuador.
- ^ "Ruby-throated hummingbird". The Ontario Hummingbird Project. 2013. Archived from the original on 20 April 2015. Retrieved 3 May 2015.
- ^ a b Williamson, S. L. (2002). A Field Guide to Hummingbirds of North America (Peterson Field Guide Series). Houghton Mifflin, Boston. ISBN 0-618-02496-4
- ^ Healy, Susan; Calder, William A. (2020). Poole, Alan F. (ed.). "Rufous hummingbird". Handbook of the Birds of the World. doi:10.2173/bow.rufhum.01. Retrieved 5 February 2018.
- ^ Vigors, Nicholas Aylward (1825). "Observations on the natural affinities that connect the orders and families of birds". Transactions of the Linnean Society of London. 14 (3): 395–517 . doi:10.1111/j.1095-8339.1823.tb00098.x.
- ^ Bock, Walter J. (1994). History and Nomenclature of Avian Family-Group Names. Bulletin of the American Museum of Natural History. Vol. Number 222. New York: American Museum of Natural History. pp. 143, 264. hdl:2246/830.
- ^ a b Mayr, Gerald (March 2005). "Fossil hummingbirds of the Old World" (PDF). Biologist. 52 (1): 12–16. Archived from the original (PDF) on 27 September 2011. Retrieved 14 December 2009.
- ^ a b c d e f g McGuire, J.; Witt, C.; Remsen, J.V.; Corl, A.; Rabosky, D.; Altshuler, D.; Dudley, R. (2014). "Molecular phylogenetics and the diversification of hummingbirds". Current Biology. 24 (8): 910–916. doi:10.1016/j.cub.2014.03.016. PMID 24704078.
- ^ Gill, Frank; Donsker, David; Rasmussen, Pamela, eds. (July 2020). "IOC World Bird List Version 10.2". International Ornithologists' Union. Retrieved 3 January 2020.
- ^ a b Mayr, Gerald (2004). "Old World fossil record of modern-type hummingbirds". Science. 304 (5672): 861–864. Bibcode:2004Sci...304..861M. doi:10.1126/science.1096856. PMID 15131303. S2CID 6845608.
- ^ Bleiweiss, Robert; Kirsch, John A. W.; Matheus, Juan Carlos (1999). "DNA-DNA hybridization evidence for subfamily structure among hummingbirds" (PDF). Auk. 111 (1): 8–19. doi:10.2307/4088500. JSTOR 4088500.
- ^ Ksepka, Daniel T.; Clarke, Julia A.; Nesbitt, Sterling J.; Kulp, Felicia B.; Grande, Lance (2013). "Fossil evidence of wing shape in a stem relative of swifts and hummingbirds (Aves, Pan-Apodiformes)". Proceedings of the Royal Society B. 280 (1761): 1761. doi:10.1098/rspb.2013.0580. PMC 3652446. PMID 23760643.
- ^ Mayr, Gerald (1 January 2007). "New specimens of the early Oligocene Old World hummingbird Eurotrochilus inexpectatus". Journal of Ornithology. 148 (1): 105–111. doi:10.1007/s10336-006-0108-y. ISSN 2193-7206. S2CID 11821178.
- ^ Bochenski, Zygmunt; Bochenski, Zbigniew M. (1 April 2008). "An Old World hummingbird from the Oligocene: a new fossil from Polish Carpathians". Journal of Ornithology. 149 (2): 211–216. doi:10.1007/s10336-007-0261-y. ISSN 2193-7206. S2CID 22193761.
- ^ a b c d "Hummingbirds' 22-million-year-old history of remarkable change is far from complete". ScienceDaily. 3 April 2014. Retrieved 30 September 2014.
- ^ a b McGuire, J.A.; Witt, C.C.; Altshuler, D.L.; Remsen, J.V. (2007). "Phylogenetic systematics and biogeography of hummingbirds: Bayesian and maximum likelihood analyses of partitioned data and selection of an appropriate partitioning strategy". Systematic Biology. 56 (5): 837–856. doi:10.1080/10635150701656360. PMID 17934998.
- ^ a b McGuire, Jimmy A.; Witt, Christopher C.; Remsen, J.V. Jr.; Dudley, R.; Altshuler, Douglas L. (2008). "A higher-level taxonomy for hummingbirds". Journal of Ornithology. 150 (1): 155–165. doi:10.1007/s10336-008-0330-x. ISSN 0021-8375. S2CID 1918245.
- ^ Dickinson, E.C.; Remsen, J.V. Jr., eds. (2013). The Howard & Moore Complete Checklist of the Birds of the World. Vol. 1: Non-passerines (4th ed.). Eastbourne, UK: Aves Press. pp. 105–136. ISBN 978-0-9568611-0-8.
- ^ Bleiweiss, R.; Kirsch, J.A.; Matheus, J.C. (1997). "DNA hybridization evidence for the principal lineages of hummingbirds (Aves:Trochilidae)". Molecular Biology and Evolution. 14 (3): 325–343. doi:10.1093/oxfordjournals.molbev.a025767. PMID 9066799.
- ^ Dickinson & Remsen 2013, pp. 105–136.
- ^ Baldwin, M.W.; Toda, Y.; Nakagita, T.; O'Connell, M.J.; Klasing, K.C.; Misaka, T.; Edwards, S.V.; Liberles, S. D. (2014). "Evolution of sweet taste perception in hummingbirds by transformation of the ancestral umami receptor". Science. 345 (6199): 929–933. Bibcode:2014Sci...345..929B. doi:10.1126/science.1255097. PMC 4302410. PMID 25146290.
- ^ Rico-Guevara, A.; Araya-Salas, M. (2015). "Bills as daggers? A test for sexually dimorphic weapons in a lekking hummingbird". Behavioral Ecology. 26 (1): 21–29. doi:10.1093/beheco/aru182.
- ^ Abrahamczyk, S.; Renner, S.S. (2015). "The temporal build-up of hummingbird/plant mutualisms in North America and temperate South America". BMC Evolutionary Biology. 15: 104. doi:10.1186/s12862-015-0388-z. PMC 4460853. PMID 26058608.
- ^ Abrahamczyk, S.; Souto-Vilarós, D.; McGuire, J.A.; Renner, S.S. (2015). "Diversity and clade ages of West Indian hummingbirds and the largest plant clades dependent on them: a 5–9 Myr young mutualistic system". Biological Journal of the Linnean Society. 114 (4): 848–859. doi:10.1111/bij.12476.
- ^ Abrahamczyk, S.; Souto-Vilaros, D.; Renner, S. S. (2014). "Escape from extreme specialization: Passionflowers, bats and the sword-billed hummingbird". Proceedings of the Royal Society B: Biological Sciences. 281 (1795): 20140888. doi:10.1098/rspb.2014.0888. PMC 4213610. PMID 25274372.
- ^ Stiles, Gary (1981). "Geographical aspects of bird flower coevolution, with particular reference to Central America" (PDF). Annals of the Missouri Botanical Garden. 68 (2): 323–351. doi:10.2307/2398801. JSTOR 2398801. S2CID 87692272.
- ^ Maglianesi, M.A.; Blüthgen, N.; Böhning-Gaese, K. & Schleuning, M. (2014). "Morphological traits determine specialization and resource use in plant–hummingbird networks in the Neotropics". Ecology. 95 (12): 3325–334. doi:10.1890/13-2261.1.
- ^ Abrahamczyk, Stefan; Poretschkin, Constantin & Renner, Susanne S. (2017). "Evolutionary flexibility in five hummingbird/plant mutualistic systems: testing temporal and geographic matching". Journal of Biogeography. 44 (8): 1847–855. doi:10.1111/jbi.12962. S2CID 90399556.
- ^ Simon, Matt (10 July 2015). "Absurd Creature of the Week: The World's Tiniest Bird Weighs Less Than a Dime". Wired. Retrieved 8 March 2017.
- ^ Dalsgaard, Bo; Martín González, Ana M.; Olesen, Jens M.; et al. (2009). "Plant-hummingbird interactions in the West Indies: Floral specialisation gradients associated with environment and hummingbird size". Oecologia. 159 (4): 757–766. Bibcode:2009Oecol.159..757D. doi:10.1007/s00442-008-1255-z. PMID 19132403. S2CID 35922888.
- ^ Rodríguez-Gironés, M.A. & Santamaría, L. (2004). "Why are so many bird flowers red?". PLOS Biology. 2 (10): e350. doi:10.1371/journal.pbio.0020350. PMC 521733. PMID 15486585.
- ^ Altschuler, D. L. (2003). "Flower color, hummingbird pollination, and habitat irradiance in four Neotropical forests". Biotropica. 35 (3): 344–355. doi:10.1646/02113. S2CID 55929111.
- ^ Nicolson, S.W. & Fleming, P.A. (2003). "Nectar as food for birds: the physiological consequences of drinking dilute sugar solutions". Plant Systematics and Evolution. 238 (1–4): 139–153. doi:10.1007/s00606-003-0276-7. S2CID 23401164.
- ^ a b Junker, Robert R.; Blüthgen, Nico; Brehm, Tanja; Binkenstein, Julia; Paulus, Justina; Martin Schaefer, H. & Stang, Martina (13 December 2012). "Specialization on traits as basis for the niche‐breadth of flower visitors and as structuring mechanism of ecological networks". Functional Ecology. 27 (2): 329–341. doi:10.1111/1365-2435.12005.
- ^ Martín González, Ana M.; Dalsgaard, Bo; et al. (30 July 2015). "The macroecology of phylogenetically structured hummingbird-plant networks". Global Ecology and Biogeography. 24 (11): 1212–224. doi:10.1111/geb.12355. hdl:10026.1/3407.
- ^ a b c d Colwell, Robert K. (1 November 2000). "Rensch's Rule Crosses the Line: Convergent Allometry of Sexual Size Dimorphism in Hummingbirds and Flower Mites". The American Naturalist. 156 (5): 495–510. doi:10.1086/303406. PMID 29587514. S2CID 4401233.
- ^ a b c Lisle, Stephen P. De; Rowe, Locke (1 November 2013). "Correlated Evolution of Allometry and Sexual Dimorphism across Higher Taxa". The American Naturalist. 182 (5): 630–639. doi:10.1086/673282. PMID 24107370. S2CID 25612107.
- ^ a b c d e f g Berns, Chelsea M.; Adams, Dean C. (11 November 2012). "Becoming Different But Staying Alike: Patterns of Sexual Size and Shape Dimorphism in Bills of Hummingbirds". Evolutionary Biology. 40 (2): 246–260. doi:10.1007/s11692-012-9206-3. ISSN 0071-3260. S2CID 276492.
- ^ a b c d e f g Temeles, Ethan J.; Miller, Jill S.; Rifkin, Joanna L. (12 April 2010). "Evolution of sexual dimorphism in bill size and shape of hermit hummingbirds (Phaethornithinae): a role for ecological causation". Philosophical Transactions of the Royal Society of London B: Biological Sciences. 365 (1543): 1053–063. doi:10.1098/rstb.2009.0284. ISSN 0962-8436. PMC 2830232. PMID 20194168.
- ^ a b "Hummingbird characteristics". learner.org. Annenberg Learner, The Annenberg Foundation. 2015. Archived from the original on 11 November 2016. Retrieved 30 August 2010.
- ^ a b c d e Williamson S (2001). A Field Guide to Hummingbirds of North America. Section: Plumage and Molt. Houghton Mifflin Harcourt. pp. 13–18. ISBN 978-0-618-02496-4.
- ^ Hamilton, W.J. (1965). "Sun-oriented display of the Anna's hummingbird" (PDF). The Wilson Bulletin. 77 (1).
- ^ a b Meadows, M.G.; Roudybush, T.E.; McGraw, K.J. (2012). "Dietary protein level affects iridescent coloration in Anna's hummingbirds, Calypte anna". Journal of Experimental Biology. 215 (16): 2742–750. doi:10.1242/jeb.069351. PMC 3404802. PMID 22837446.
- ^ a b c d Hightower, Ben J.; Wijnings, Patrick W.A.; Scholte, Rick; et al. (16 March 2021). "How oscillating aerodynamic forces explain the timbre of the hummingbird's hum and other animals in flapping flight". eLife. 10: e63107. doi:10.7554/elife.63107. ISSN 2050-084X. PMC 8055270. PMID 33724182.
- ^ a b Eindhoven University of Technology (16 March 2021). "New measurement technique unravels what gives hummingbird wings their characteristic sound". Phys.org. Retrieved 13 May 2021.
- ^ Ingersoll, Rivers; Lentink, David (15 October 2018). "How the hummingbird wingbeat is tuned for efficient hovering". Journal of Experimental Biology. 221 (20). doi:10.1242/jeb.178228. ISSN 1477-9145. PMID 30323114.
- ^ Ocampo, Diego; Barrantes, Gilbert; Uy, J. Albert C. (27 September 2018). "Morphological adaptations for relatively larger brains in hummingbird skulls". Ecology and Evolution. 8 (21): 10482–10488. doi:10.1002/ece3.4513. ISSN 2045-7758. PMC 6238128. PMID 30464820.
- ^ a b c d Lisney, T.J.; Wylie, D.R.; Kolominsky, J.; Iwaniuk, A.N. (2015). "Eye morphology and retinal topography in hummingbirds (Trochilidae Aves)". Brain, Behavior and Evolution. 86 (3–4): 176–190. doi:10.1159/000441834. PMID 26587582.
- ^ Iwaniuk, A.N.; Wylie, D.R. (2007). "Neural specialization for hovering in hummingbirds: hypertrophy of the pretectal nucleus Lentiformis mesencephali" (PDF). Journal of Comparative Neurology. 500 (2): 211–221. doi:10.1002/cne.21098. PMID 17111358. S2CID 15678218.
- ^ a b c d Gaede, A.H.; Goller, B.; Lam, J.P.; Wylie, D.R.; Altshuler, D.L. (2017). "Neurons responsive to global visual motion have unique tuning properties in hummingbirds". Current Biology. 27 (2): 279–285. doi:10.1016/j.cub.2016.11.041. PMID 28065606. S2CID 28314419.
- ^ a b "Hummingbirds see motion in an unexpected way". ScienceDaily. 5 January 2017. Retrieved 24 April 2017.
- ^ a b Stoddard, M.C.; Eyster, H.N.; Hogan, B.G.; et al. (15 June 2020). "Wild hummingbirds discriminate nonspectral colors". Proceedings of the National Academy of Sciences. 117 (26): 15112–122. doi:10.1073/pnas.1919377117. ISSN 0027-8424. PMC 7334476. PMID 32541035.
- ^ a b c d Goller, B.; Altshuler, D.L. (2014). "Hummingbirds control hovering flight by stabilizing visual motion". Proceedings of the National Academy of Sciences. 111 (51): 18375–380. Bibcode:2014PNAS..11118375G. doi:10.1073/pnas.1415975111. PMC 4280641. PMID 25489117.
- ^ Altshuler, D.L.; Dudley, R. (2002). "The ecological and evolutionary interface of hummingbird flight physiology". The Journal of Experimental Biology. 205 (Pt 16): 2325–336. doi:10.1242/jeb.205.16.2325. PMID 12124359.
- ^ Suarez R.K.; Lighton J.R.; Brown G.S.; Mathieu-Costello O. (June 1991). "Mitochondrial respiration in hummingbird flight muscles". Proceedings of the National Academy of Sciences of the United States of America. 88 (11): 4870–3. doi:10.1073/pnas.88.11.4870. PMC 51768. PMID 2052568.
- ^ Welch, K.C. Jr.; Chen, C.C. (2014). "Sugar flux through the flight muscles of hovering vertebrate nectarivores: A review". Journal of Comparative Physiology B. 184 (8): 945–959. doi:10.1007/s00360-014-0843-y. PMID 25031038. S2CID 11109453.
- ^ a b Chen, Chris Chin Wah; Welch, Kenneth Collins (2014). "Hummingbirds can fuel expensive hovering flight completely with either exogenous glucose or fructose". Functional Ecology. 28 (3): 589–600. doi:10.1111/1365-2435.12202.
- ^ Welch, K.C. Jr.; Suarez, R.K. (2007). "Oxidation rate and turnover of ingested sugar in hovering Anna's (Calypte anna) and rufous (Selasphorus rufus) hummingbirds". Journal of Experimental Biology. 210 (Pt 12): 2154–162. doi:10.1242/jeb.005363. PMID 17562889.
- ^ Suarez, Raul; Welch, Kenneth (12 July 2017). "Sugar metabolism in hummingbirds and nectar bats". Nutrients. 9 (7): 743. doi:10.3390/nu9070743. ISSN 2072-6643. PMC 5537857. PMID 28704953.
- ^ a b Callier, Viviane (24 February 2023). "Evolution Turns These Knobs to Make a Hummingbird Hyperquick and a Cavefish Sluggishly Slow". Scientific American. Retrieved 27 February 2023.
- ^ a b Osipova, Ekaterina; Barsacchi, Rico; Brown, Tom; et al. (13 January 2023). "Loss of a gluconeogenic muscle enzyme contributed to adaptive metabolic traits in hummingbirds". Science. 379 (6628): 185–190. doi:10.1126/science.abn7050. ISSN 0036-8075.
- ^ a b c Hargrove, J.L. (2005). "Adipose energy stores, physical work, and the metabolic syndrome: Lessons from hummingbirds". Nutrition Journal. 4: 36. doi:10.1186/1475-2891-4-36. PMC 1325055. PMID 16351726.
- ^ Skutch, Alexander F. & Singer, Arthur B. (1973). The Life of the Hummingbird. New York: Crown Publishers. ISBN 978-0-517-50572-4.
- ^ Lasiewski, Robert C. (1964). "Body temperatures, heart and breathing rate, and evaporative water loss in hummingbirds". Physiological Zoology. 37 (2): 212–223. doi:10.1086/physzool.37.2.30152332. S2CID 87037075.
- ^ a b Projecto-Garcia, Joana; Natarajan, Chandrasekhar; Moriyama, Hideaki; et al. (2 December 2013). "Repeated elevational transitions in hemoglobin function during the evolution of Andean hummingbirds". Proceedings of the National Academy of Sciences of the United States of America. 110 (51): 20669–20674. Bibcode:2013PNAS..11020669P. doi:10.1073/pnas.1315456110. ISSN 0027-8424. PMC 3870697. PMID 24297909.
- ^ a b "How do hummingbirds thrive in the Andes?". The Guardian. 13 December 2013. Retrieved 15 August 2022.
- ^ Lim, Marisa C.W.; Witt, Christopher C.; Graham, Catherine H.; Dávalos, Liliana M. (22 May 2019). "Parallel molecular evolution in pathways, genes, and sites in high-elevation hummingbirds revealed by comparative transcriptomics". Genome Biology and Evolution. 11 (6): 1573–1585. doi:10.1093/gbe/evz101. ISSN 1759-6653. PMC 6553505. PMID 31114863.
- ^ Gayman, Deann (2 December 2013). "New study reveals how hummingbirds evolved to fly at high altitude". Department of Communication and Marketing, University of Nebraska-Lincoln. Retrieved 15 August 2022.
- ^ a b c d Powers, Donald R.; Langland, Kathleen M.; Wethington, Susan M.; Powers, Sean D.; Graham, Catherine H.; Tobalske, Bret W. (2017). "Hovering in the heat: effects of environmental temperature on heat regulation in foraging hummingbirds". Royal Society Open Science. 4 (12): 171056. doi:10.1098/rsos.171056. ISSN 2054-5703. PMC 5750011. PMID 29308244.
- ^ Evangelista, Dennis; Fernández, María José; Berns, Madalyn S.; Hoover, Aaron; Dudley, Robert (2010). "Hovering energetics and thermal balance in Anna's hummingbirds (Calypte anna)". Physiological and Biochemical Zoology. 83 (3): 406–413. doi:10.1086/651460. ISSN 1522-2152. PMID 20350142. S2CID 26974159.
- ^ Soniak, Matt (2 February 2016). "Infrared video shows how hummingbirds shed heat through their eyes and feet". Mental Floss. Retrieved 14 January 2020.
- ^ a b Udvardy, Miklos D.F. (1983). "The role of the feet in behavioral thermoregulation of hummingbirds" (PDF). Condor. 85 (3): 281–285. doi:10.2307/1367060. JSTOR 1367060.
- ^ Suarez, R.K.; Gass, C.L. (2002). "Hummingbirds foraging and the relation between bioenergetics and behavior". Comparative Biochemistry and Physiology. Part A. 133 (2): 335–343. doi:10.1016/S1095-6433(02)00165-4. PMID 12208304.
- ^ a b c d e Bakken, B.H.; McWhorter, T.J.; Tsahar, E.; Martinez del Rio, C. (2004). "Hummingbirds arrest their kidneys at night: diel variation in glomerular filtration rate in Selasphorus platycercus". The Journal of Experimental Biology. 207 (25): 4383–391. doi:10.1242/jeb.01238. PMID 15557024.
- ^ a b c Bakken, B.H.; Sabat, P. (2006). "Gastrointestinal and renal responses to water intake in the green-backed firecrown (Sephanoides sephanoides), a South American hummingbird". AJP: Regulatory, Integrative and Comparative Physiology. 291 (3): R830–836. doi:10.1152/ajpregu.00137.2006. hdl:10533/177203. PMID 16614056. S2CID 2391784.
- ^ Lotz, Chris N.; Martínez Del Rio, Carlos (2004). "The ability of rufous hummingbirds Selasphorus rufus to dilute and concentrate urine". Journal of Avian Biology. 35: 54–62. doi:10.1111/j.0908-8857.2004.03083.x.
- ^ Beuchat, C.A.; Preest, M.R.; Braun, E.J. (1999). "Glomerular and medullary architecture in the kidney of Anna's Hummingbird". Journal of Morphology. 240 (2): 95–100. doi:10.1002/(sici)1097-4687(199905)240:2<95::aid-jmor1>3.0.co;2-u. PMID 29847878. S2CID 44156688.
- ^ a b c d e f g Duque, F.G.; Carruth, L.L. (2022). "Vocal communication in hummingbirds". Brain, Behavior and Evolution (Review). 97 (3–4): 241–252. doi:10.1159/000522148. PMID 35073546.
- ^ "Song sounds of various hummingbird species". All About Birds. The Cornell Lab of Ornithology, Cornell University, Ithaca, New York. 2015. Retrieved 25 June 2016.
- ^ a b c Pytte, C.L.; Ficken, M.S.; Moiseff, A. (2004). "Ultrasonic singing by the blue-throated hummingbird: A comparison between production and perception". Journal of Comparative Physiology A. 190 (8): 665–673. doi:10.1007/s00359-004-0525-4. PMID 15164219. S2CID 7231117.
- ^ a b c Duque, F.G.; Rodríguez-Saltos, C.A.; Wilczynsk, W. (September 2018). "High-frequency vocalizations in Andean hummingbirds". Current Biology. 28 (17): R927–R928. doi:10.1016/j.cub.2018.07.058. PMID 30205060.
- ^ a b Monte, Amanda; Cerwenka, Alexander F.; Ruthensteiner, Bernhard; Gahr, Manfred; Düring, Daniel N. (6 July 2020). "The hummingbird syrinx morphome: a detailed three-dimensional description of the black jacobin's vocal organ". BMC Zoology. 5 (1): 7. doi:10.1186/s40850-020-00057-3. ISSN 2056-3132. S2CID 220509046.
- ^ Riede, Tobias; Olson, Christopher R. (6 February 2020). "The vocal organ of hummingbirds shows convergence with songbirds". Scientific Reports. 10 (1): 2007. Bibcode:2020NatSR..10.2007R. doi:10.1038/s41598-020-58843-5. ISSN 2045-2322. PMC 7005288. PMID 32029812.
- ^ a b c Jarvis, Erich D.; Ribeiro, Sidarta; da Silva, Maria Luisa; Ventura, Dora; Vielliard, Jacques; Mello, Claudio V. (2000). "Behaviourally driven gene expression reveals song nuclei in hummingbird brain". Nature. 406 (6796): 628–632. Bibcode:2000Natur.406..628J. doi:10.1038/35020570. PMC 2531203. PMID 10949303.
- ^ Gahr M. (2000). "Neural song control system of hummingbirds: comparison to swifts, vocal learning (Songbirds) and nonlearning (Suboscines) passerines, and vocal learning (Budgerigars) and nonlearning (Dove, owl, gull, quail, chicken) nonpasserines". J Comp Neurol. 486 (2): 182–196. doi:10.1002/1096-9861(20001016)426:2<182::AID-CNE2>3.0.CO;2-M. PMID 10982462. S2CID 10763166.
- ^ Renne, Paul R.; Deino, Alan L.; Hilgen, Frederik J.; et al. (7 February 2013). "Time Scales of Critical Events Around the Cretaceous-Paleogene Boundary" (PDF). Science. 339 (6120): 684–687. Bibcode:2013Sci...339..684R. doi:10.1126/science.1230492. PMID 23393261. S2CID 6112274. Archived from the original (PDF) on 7 February 2017. Retrieved 1 April 2018.
- ^ Hainsworth, F.R.; Wolf, L.L. (1970). "Regulation of oxygen consumption and body temperature during torpor in a hummingbird, Eulampis jugularis". Science. 168 (3929): 368–369. Bibcode:1970Sci...168..368R. doi:10.1126/science.168.3929.368. PMID 5435893. S2CID 30793291.
- ^ Hiebert, S.M. (1992). "Time-dependent thresholds for torpor initiation in the rufous hummingbird (Selasphorus rufus)". Journal of Comparative Physiology B. 162 (3): 249–255. doi:10.1007/bf00357531. PMID 1613163. S2CID 24688360.
- ^ a b c Wolf, Blair O.; McKechnie, Andrew E.; Schmitt, C. Jonathan; Czenze, Zenon J.; Johnson, Andrew B.; Witt, Christopher C. (2020). "Extreme and variable torpor among high-elevation Andean hummingbird species". Biology Letters of the Royal Society. 16 (9): 20200428. doi:10.1098/rsbl.2020.0428. ISSN 1744-9561. PMC 7532710. PMID 32898456.
- ^ Greenwood, Veronique (8 September 2020). "These hummingbirds take extreme naps. Some may even hibernate". The New York Times. ISSN 0362-4331. Retrieved 9 September 2020.
- ^ Hiebert, S.M.; Salvante, K.G.; Ramenofsky, M.; Wingfield, J.C. (2000). "Corticosterone and nocturnal torpor in the rufous hummingbird (Selasphorus rufus)". General and Comparative Endocrinology. 120 (2): 220–234. doi:10.1006/gcen.2000.7555. PMID 11078633.
- ^ Powers, D.R.; Brown, A.R.; Van Hook, J.A. (2003). "Influence of normal daytime fat deposition on laboratory measurements of torpor use in territorial versus nonterritorial hummingbirds". Physiological and Biochemical Zoology. 76 (3): 389–397. doi:10.1086/374286. PMID 12905125. S2CID 6475160.
- ^ a b Shankar, Anusha; Schroeder, Rebecca J.; Wethington, Susan M.; Graham, Catherine H.; Powers, Donald R. (May 2020). "Hummingbird torpor in context: duration, more than temperature, is the key to nighttime energy savings". Journal of Avian Biology. 51 (5): jav.02305. doi:10.1111/jav.02305. ISSN 0908-8857. S2CID 216458501.
- ^ a b "The hummingbird project of British Columbia". Rocky Point Bird Observatory, Vancouver Island, British Columbia. 2010. Retrieved 25 June 2016.
- ^ Churchfield, Sara (1990). The natural history of shrews. Cornell University Press. pp. 35–37. ISBN 978-0-8014-2595-0.
- ^ "Longevity Records Of North American Birds". United States Geological Survey. Retrieved 26 January 2021.
- ^ Patuxent Wildlife Research Center, Bird Banding Laboratory. Longevity Records AOU Numbers 3930–4920 2009-08-31. Retrieved 2009-09-27.
- ^ Fisher, R. Jr. (1994). "Praying mantis catches and eats hummingbird". Birding. 26: 376.
- ^ Lorenz, S. (2007). "Carolina mantid (Stagmomantis carolina) captures and feeds on a broad-tailed hummingbird (Selasphorus platycercus)". Bulletin of the Texas Ornithological Society. 40: 37–38.
- ^ Nyffeler, Martin; Maxwell, Michael R.; Remsen, J.V. (2017). "Bird predation by praying mantises: A global perspective". The Wilson Journal of Ornithology. 129 (2): 331–344. doi:10.1676/16-100.1. ISSN 1559-4491. S2CID 90832425.
- ^ Stiteler, Sharon (29 October 2015). "Which animals prey on hummingbirds?". National Audubon Society. Retrieved 4 November 2021.
- ^ a b c d Oniki, Y; Willis, E.O. (2000). "Nesting behavior of the swallow-tailed hummingbird, Eupetomena macroura (Trochilidae, Aves)". Brazilian Journal of Biology. 60 (4): 655–662. doi:10.1590/s0034-71082000000400016. PMID 11241965.
- ^ a b c d "Hummingbird nesting". Public Broadcasting System – Nature; from Learner.org, Journey North. 2016. Archived from the original (video) on 2 February 2017. Retrieved 12 May 2016.
- ^ a b c "Hummingbird Q&A: Nest and eggs". Operation Rubythroat: The Hummingbird Project, Hilton Pond Center for Piedmont Natural History. 2014. Retrieved 21 June 2014.
- ^ Mohrman, Eric (22 November 2019). "How do hummingbirds mate?". Sciencing, Leaf Group Media. Retrieved 8 February 2020.
- ^ a b c Warrick, Douglas R.; Tobalske, Bret W.; Powers, Donald R. (2005). "Aerodynamics of the hovering hummingbird". Nature. 435 (7045): 1094–097. Bibcode:2005Natur.435.1094W. doi:10.1038/nature03647. PMID 15973407. S2CID 4427424.
- ^ Sapir, N.; Dudley, R. (2012). "Backward flight in hummingbirds employs unique kinematic adjustments and entails low metabolic cost". Journal of Experimental Biology. 215 (20): 3603–611. doi:10.1242/jeb.073114. PMID 23014570.
- ^ Tobalske, Bret W.; Warrick, Douglas R.; Clark, Christopher J.; Powers, Donald R.; Hedrick, Tyson L.; Hyder, Gabriel A.; Biewener, Andrew A. (2007). "Three-dimensional kinematics of hummingbird flight". J Exp Biol. 210 (13): 2368–382. doi:10.1242/jeb.005686. PMID 17575042.
- ^ University of California - Riverside (25 February 2013). "Study shows hovering hummingbirds generate two trails of vortices under their wings, challenging one-vortex consensus". Phys.org. Retrieved 8 March 2023.
- ^ Pournazeri, Sam; Segre, Paolo S.; Princevac, Marko; Altshuler, Douglas L. (25 December 2012). "Hummingbirds generate bilateral vortex loops during hovering: evidence from flow visualization". Experiments in Fluids. 54 (1): 1439. doi:10.1007/s00348-012-1439-5. ISSN 0723-4864.
- ^ Tobalske, B.W.; Biewener, A.A.; Warrick, D.R.; Hedrick, T.L.; Powers, D.R. (2010). "Effects of flight speed upon muscle activity in hummingbirds". Journal of Experimental Biology. 213 (14): 2515–523. doi:10.1242/jeb.043844. PMID 20581281.
- ^ Videler, J.J. (2005). Avian Flight. Oxford University Press, Ornithology Series. p. 34. ISBN 978-0-19-856603-8.
- ^ Fernández, M.J.; Dudley, R.; Bozinovic, F. (2011). "Comparative energetics of the giant hummingbird (Patagona gigas)". Physiological and Biochemical Zoology. 84 (3): 333–340. doi:10.1086/660084. PMID 21527824. S2CID 31616893.
- ^ Gill, V. (30 July 2014). "Hummingbirds edge out helicopters in hover contest". BBC News. Retrieved 1 September 2014.
- ^ Feinsinger, Peter; Colwell, Robert K.; Terborgh, John; Chaplin, Susan Budd (1979). "Elevation and the Morphology, Flight Energetics, and Foraging Ecology of Tropical Hummingbirds". The American Naturalist. 113 (4): 481–497. doi:10.1086/283408. ISSN 0003-0147. S2CID 85317341.
- ^ Morelle, R. (8 November 2011). "Hummingbirds shake their heads to deal with rain". BBC News. Retrieved 22 March 2014.
- ^ St. Fleur, N. (20 July 2012). "Hummingbird rain trick: New study shows tiny birds alter posture in storms" (video). Huffington Post. Retrieved 22 March 2014.
- ^ Steen, Ronny; Kagge, Erik Olfert; Lilleengen, Petter; Lindemann, Jon Peder; Midtgaard, Fred (2020). "Wingbeat frequencies in free-ranging hummingbirds in Costa Rica and Ecuador". Cotinga. 42: 3–8.
- ^ Clark, C.J. (2011). "Wing, tail, and vocal contributions to the complex acoustic signals of courting Calliope hummingbirds". Current Zool. 57 (2): 187–196. doi:10.1093/czoolo/57.2.187.
- ^ a b c Ravi, Sridhar; Crall, James D.; McNeilly, Lucas; Gagliardi, Susan F.; Biewener, Andrew A.; Combes, Stacey A. (2015). "Hummingbird flight stability and control in freestream turbulent winds". J Exp Biol. 218 (Pt 9): 1444–452. doi:10.1242/jeb.114553. PMID 25767146.
- ^ a b c d Clark, C.J. (2009). "Courtship dives of Anna's hummingbird offer insights into flight performance limits". Proceedings of the Royal Society B: Biological Sciences. 276 (1670): 3047–052. doi:10.1098/rspb.2009.0508. PMC 2817121. PMID 19515669.
- ^ Akparibo, Issaka Y.; Anderson, Jackie; Chumbley, Eric (7 September 2020). "Aerospace Gravitational Effects". Aerospace, gravitational effects, high performance. National Center for Biotechnology Information, US National Institute of Medicine. PMID 28613519.
- ^ a b c Clark, C. J.; Feo, T.J. (2008). "The Anna's hummingbird chirps with its tail: A new mechanism of sonation in birds". Proceedings of the Royal Society B: Biological Sciences. 275 (1637): 955–962. doi:10.1098/rspb.2007.1619. PMC 2599939. PMID 18230592.
- ^ a b Clark, C.J. (2014). "Harmonic hopping, and both punctuated and gradual evolution of acoustic characters in Selasphorus hummingbird tail-feathers". PLOS ONE. 9 (4): e93829. Bibcode:2014PLoSO...993829C. doi:10.1371/journal.pone.0093829. PMC 3983109. PMID 24722049.
- ^ Clark, C. J.; Feo, T. J. (2010). "Why do Calypte hummingbirds "sing" with both their tail and their syrinx? An apparent example of sexual sensory bias". The American Naturalist. 175 (1): 27–37. doi:10.1086/648560. PMID 19916787. S2CID 29680714.
- ^ Clark, C.J.; Elias, D.O.; Prum, R.O. (2013). "Hummingbird feather sounds are produced by aeroelastic flutter, not vortex-induced vibration". Journal of Experimental Biology. 216 (18): 3395–403. doi:10.1242/jeb.080317. PMID 23737562.
- ^ Clark, C.J. (2011). "Wing, tail, and vocal contributions to the complex acoustic signals of courting Calliope hummingbirds" (PDF). Current Zoology. 57 (2): 187–196. doi:10.1093/czoolo/57.2.187. Archived from the original (PDF) on 16 July 2015. Retrieved 31 May 2015.
- ^ Kovacevic, M. (30 January 2008). "Hummingbird sings with its tail feathers". Cosmos Magazine. Archived from the original on 3 May 2012. Retrieved 13 July 2013.
- ^ a b c Miller, Sarah J.; Inouye, David W. (1983). "Roles of the Wing Whistle in the Territorial Behaviour of Male Broad-tailed Hummingbirds (Selasphorus platycercus)". Animal Behaviour. 31 (3): 689–700. doi:10.1016/S0003-3472(83)80224-3. S2CID 53160649. Retrieved 13 July 2014 – via hummingbirds.net.
- ^ a b Lowe, Joe (12 September 2019). "Do hummingbirds migrate?". American Bird Conservancy. Retrieved 8 March 2023.
- ^ Godshalk, Katrina. "Hummingbird migration". High Country Gardens. Retrieved 16 January 2023.
- ^ a b López-Segoviano, Gabriel; Arenas-Navarro, Maribel; Vega, Ernesto; Arizmendi, Maria del Coro (2018). "Hummingbird migration and flowering synchrony in the temperate forests of northwestern Mexico". Peerj. 6: e5131. doi:10.7717/peerj.5131. PMC 6037137. PMID 30002968.
- ^ a b c d e f g "Hummingbird Migration". Hummingbird Central. 2018. Retrieved 28 August 2018.
- ^ "Migration and Range Maps". The Ontario Hummingbird Project. 2013. Archived from the original on 3 April 2014. Retrieved 23 March 2014.
- ^ a b c d e f "Rufous Hummingbird". Cornell University Laboratory of Ornithology. 2014. Retrieved 10 April 2014.
- ^ "Hummingbird news: Tracking migration". Journey North, Annenberg Learner, learner.org. Archived from the original on 7 March 2017. Retrieved 22 March 2014.
- ^ McKinney, A.M.; Caradonna, P.J.; Inouye, D.W.; Barr, B; Bertelsen, C.D.; Waser, N.M. (2012). "Asynchronous changes in phenology of migrating broad-tailed hummingbirds and their early-season nectar resources" (PDF). Ecology. 93 (9): 1987–993. doi:10.1890/12-0255.1. PMID 23094369.
- ^ Altshuler, D.L.; Dudley, R. (2002). "The ecological and evolutionary interface of hummingbird flight physiology". The Journal of Experimental Biology. 205 (Pt 16): 2325–336. doi:10.1242/jeb.205.16.2325. PMID 12124359.
- ^ a b Yanega, Gregor M.; Rubega, Margaret A. (2004). "Feeding mechanisms: Hummingbird jaw bends to aid insect capture". Nature. 428 (6983): 615. Bibcode:2004Natur.428..615Y. doi:10.1038/428615a. PMID 15071586. S2CID 4423676.
- ^ a b c "Hummingbirds catch flying bugs with the help of fast-closing beaks". ScienceDaily. 20 July 2011. Retrieved 10 May 2017.
- ^ a b c Connor, J. (15 October 2010). "Not All Sweetness and Light". Cornell University, Laboratory of Ornithology, Allaboutbirds.org, Ithaca, NY. Archived from the original on 16 July 2015. Retrieved 24 January 2011.
- ^ Unwin, Mike (2011). The Atlas of Birds: Diversity, Behavior, and Conservation. Princeton University Press. p. 57. ISBN 978-1-4008-3825-7.
- ^ Stevens, C. Edward; Hume, Ian D. (2004). Comparative Physiology of the Vertebrate Digestive System. Cambridge University Press. p. 126. ISBN 978-0-521-61714-7.
- ^ Diamond, Jared M.; Karasov, William H.; Phan, Duong; Carpenter, F. Lynn (1986). "Digestive physiology is a determinant of foraging bout frequency in hummingbirds". Nature. 320 (6057): 62–3. doi:10.1038/320062a0. PMID 3951548.
- ^ Ward, B.J.; Day, L.B.; Wilkening, S.R.; et al. (2012). "Hummingbirds have a greatly enlarged hippocampal formation". Biology Letters. 8 (4): 657–659. doi:10.1098/rsbl.2011.1180. PMC 3391440. PMID 22357941.
- ^ "Fiery-tailed awlbills". Beauty of Birds. 16 September 2021. Retrieved 8 March 2023.
- ^ Temeles, E.J. (1996). "A new dimension to hummingbird-flower relationships". Oecologia. 105 (4): 517–523. Bibcode:1996Oecol.105..517T. doi:10.1007/bf00330015. PMID 28307145. S2CID 31641494.
- ^ a b c Baldwin, Maude W.; Toda, Yasuka; Nakagita, Tomoya; O'Connell, Mary J.; Klasing, Kirk C.; Misaka, Takumi; Edwards, Scott V.; Liberles, Stephen D. (2014). "Sensory biology. Evolution of sweet taste perception in hummingbirds by transformation of the ancestral umami receptor". Science. 345 (6199): 929–933. Bibcode:2014Sci...345..929B. doi:10.1126/science.1255097. PMC 4302410. PMID 25146290.
- ^ Li, X. (2009). "T1R receptors mediate mammalian sweet and umami taste". American Journal of Clinical Nutrition. 90 (3): 733S–37S. doi:10.3945/ajcn.2009.27462G. PMID 19656838.
- ^ a b c d Rico-Guevara, Alejandro; Fan, Tai-Hsi; Rubega, Margaret A. (22 August 2015). "Hummingbird tongues are elastic micropumps". Proceedings of the Royal Society B. 282 (1813): 20151014. doi:10.1098/rspb.2015.1014. ISSN 0962-8452. PMC 4632618. PMID 26290074.
- ^ a b c d Frank, David; Gorman, James (8 September 2015). "ScienceTake | The hummingbird's tongue". The New York Times. ISSN 0362-4331. Retrieved 10 September 2015.
- ^ a b Kim, W.; Peaudecerf, F.; Baldwin, M.W.; Bush, J.W. (2012). "The hummingbird's tongue: A self-assembling capillary syphon". Proceedings of the Royal Society B: Biological Sciences. 279 (1749): 4990–996. doi:10.1098/rspb.2012.1837. PMC 3497234. PMID 23075839.
- ^ Rico-Guevara, A.; Rubega, M.A. (2011). "The hummingbird tongue is a fluid trap, not a capillary tube". Proceedings of the National Academy of Sciences. 108 (23): 9356–360. Bibcode:2011PNAS..108.9356R. doi:10.1073/pnas.1016944108. PMC 3111265. PMID 21536916.
- ^ a b Mosher, D. (2 May 2011). "High-speed video shows how hummingbirds really drink". Wired. Retrieved 13 August 2022.
- ^ Gorman, James (8 September 2015). "The hummingbird's tongue: How it works". The New York Times. ISSN 0362-4331. Retrieved 10 September 2015.
- ^ Stahl, J.M.; Nepi, M.; Galetto, L.; Guimarães, E.; Machado, S.R. (2012). "Functional aspects of floral nectar secretion of Ananas ananassoides, an ornithophilous bromeliad from the Brazilian savanna". Annals of Botany. 109 (7): 1243–252. doi:10.1093/aob/mcs053. PMC 3359915. PMID 22455992.
- ^ Avalos, G.; Soto, A.; Alfaro, W. (2012). "Effect of artificial feeders on pollen loads of the hummingbirds of Cerro de la Muerte, Costa Rica". Revista de Biología Tropical. 60 (1): 65–73. doi:10.15517/rbt.v60i1.2362. PMID 22458209.
- ^ "Hummingbird Nectar Recipe". Nationalzoo.si.edu. Retrieved 7 September 2022.
- ^ Rousseu, F.; Charette, Y.; Bélisle, M. (2014). "Resource defense and monopolization in a marked population of ruby-throated hummingbirds (Archilochus colubris)". Ecology and Evolution. 4 (6): 776–793. doi:10.1002/ece3.972. PMC 3967903. PMID 24683460.
- ^ "How to Make Hummingbird Nectar". Audubon.com. Audubon Society. 14 April 2016.
- ^ "Feeding Hummingbirds". www.kern.audubon.org. Audubon California Kern River Preserve.
- ^ "Feeders and Feeding Hummingbirds". Faq.gardenweb.com. 9 January 2008. Retrieved 25 January 2009.
- ^ "Hummingbird F.A.Q.s from the Southeastern Arizona Bird Observatory". Sabo.org. 25 November 2008. Archived from the original on 2 November 2014. Retrieved 25 January 2009.
- ^ Attracting Hummingbirds |Missouri Department of Conservation Archived 19 April 2012 at the Wayback Machine Retrieved on 2013-04-01
- ^ a b Chambers, Lanny (2016). "Please Don't Use Red Dye". Hummingbirds.net. Retrieved 25 June 2016.
- ^ "Should I Add Red Dye to My Hummingbird Food?". Trochilids.com. Retrieved 20 March 2010.
- ^ a b "Hummingbirds See Red". US National Audubon Society. 28 May 2013. Retrieved 23 April 2017.
- ^ "Hummingbirds take no notice of flower color". Phys.org. 16 March 2012. Retrieved 22 April 2017.
- ^ Hurly, T.A.; Franz, S; Healy, S.D. (2010). "Do rufous hummingbirds (Selasphorus rufus) use visual beacons?". Animal Cognition. 13 (2): 377–383. doi:10.1007/s10071-009-0280-6. PMID 19768647. S2CID 9189780.
- ^ Hurly, T.A.; Fox, T.A.O.; Zwueste, D.M.; Healy, S.D. (2014). "Wild hummingbirds rely on landmarks not geometry when learning an array of flowers" (PDF). Animal Cognition. 17 (5): 1157–165. doi:10.1007/s10071-014-0748-x. hdl:10023/6422. PMID 24691650. S2CID 15169177.
- ^ Hornsby, Mark A.W.; Healy, Susan D.; Hurly, T. Andrew (2017). "Wild hummingbirds can use the geometry of a flower array". Behavioural Processes. 139: 33–37. doi:10.1016/j.beproc.2017.01.019. ISSN 0376-6357. PMID 28161360.
- ^ a b c Herrera, G; Zagal, J. C.; Diaz, M; Fernández, M. J.; Vielma, A; Cure, M; Martinez, J; Bozinovic, F; Palacios, A. G. (2008). "Spectral sensitivities of photoreceptors and their role in colour discrimination in the green-backed firecrown hummingbird (Sephanoides sephaniodes)". Journal of Comparative Physiology A. 194 (9): 785–794. doi:10.1007/s00359-008-0349-8. hdl:10533/142104. PMID 18584181. S2CID 7491787.
- ^ Kim, Ashley Y.; Rankin, David T.; Rankin, Erin E. Wilson (2021). "What is that smell? Hummingbirds avoid foraging on resources with defensive insect compounds". Behavioral Ecology and Sociobiology. 75 (9): 132. doi:10.1007/s00265-021-03067-4. ISSN 0340-5443.
- ^ Werness, Hope B.; Benedict, Joanne H.; Thomas, Scott; Ramsay-Lozano, Tiffany (2004). The Continuum Encyclopedia of Animal Symbolism in Art. Continuum International Publishing Group. p. 229. ISBN 978-0-8264-1525-7.
- ^ a b c "Huitzilopochtli". Encyclopaedia Britannica. 2023. Retrieved 5 March 2023.
- ^ MacDonald, Fiona (2008). How to Be an Aztec Warrior. National Geographic Books. p. 25. ISBN 978-1-4263-0168-1.
- ^ Golomb, Jason (28 September 2019). "Nasca lines". National Geographic. Retrieved 5 March 2023.
- ^ "National Symbols of Trinidad and Tobago". National Library of Trinidad and Tobago, Port of Spain. 2016. Archived from the original on 7 May 2016. Retrieved 18 April 2016.
- ^ "Coins of Trinidad and Tobago". Central Bank of Trinidad and Tobago, Port of Spain. 2015. Archived from the original on 7 February 2017. Retrieved 18 April 2016.
- ^ "Brand Refresh: Introducing the new Caribbean Airlines". Caribbean Airlines. 1 March 2020. Retrieved 5 March 2023.
- ^ "Sierra Azul Preserve - Overview". Midpeninsula Regional Open Space District. 2021. Retrieved 5 March 2023.
- ^ Stanton, Kristen M. (31 May 2020). "Hummingbird meaning and symbolism". UniGuide.
- ^ "Hummingbird Original". Gibson Brands, Inc. 2023. Retrieved 5 March 2023.
- ^ "Connie Jiménez dressed as a hummingbird in the Miss Universe preliminary competition (translated from Spanish)". El Commercio. 26 January 2017. Retrieved 5 March 2023.
- The Hummingbird Website Hummingbird photos, videos, articles, links, frequently asked questions
- High-resolution photo gallery of almost 100 species
- High-resolution photo gallery of many species of hummingbirds
- Video of hummingbird tongue acting as a micropump during nectar feeding