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Hummingbirds are
bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
s native to the
Americas The Americas, which are sometimes collectively called America, are a landmass comprising the totality of North and South America. The Americas make up most of the land in Earth's Western Hemisphere and comprise the New World. Along with t ...
and comprise the
biological family Family ( la, familia, plural ') is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between order and genus. A family may be divided into subfamilies, which are intermediate ranks between the ranks of ...
Trochilidae. With about 361 species and 113 genera, they occur from
Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U. ...
to
Tierra del Fuego Tierra del Fuego (, ; Spanish for "Land of the Fire", rarely also Fireland in English) is an archipelago off the southernmost tip of the South American mainland, across the Strait of Magellan. The archipelago consists of the main island, Isla ...
, but the vast majority of the species are found in the
tropics The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referre ...
around the equator. They are small birds, with most species measuring in length. The smallest extant hummingbird species is the bee hummingbird, which weighs less than . The largest hummingbird species is the
giant hummingbird The giant hummingbird (''Patagona gigas'') is the only member of the genus ''Patagona'' and the largest member of the hummingbird family, weighing and having a wingspan of approximately and length of . This is approximately the same length as ...
, weighing . They are specialized for feeding on flower nectar, but all species also consume flying insects or spiders. Hummingbirds split from their
sister group In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...
, 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. They are known as hummingbirds because of the humming sound created by their beating
wings A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is expres ...
, which flap at high frequencies audible to humans. They hover in mid-air at rapid wing-flapping rates, which vary from around 12 beats per second in the largest species to around 80 per second in small hummingbirds. Of those species that have been measured during flying in wind tunnels, their top speeds exceed . During courtship, some male species dive from of height above a female at speeds around . Hummingbirds have the highest mass-specific metabolic rate of any
homeothermic Homeothermy, homothermy or homoiothermy is thermoregulation that maintains a stable internal body temperature regardless of external influence. This internal body temperature is often, though not necessarily, higher than the immediate environme ...
animal. To conserve energy when food is scarce and at night when not foraging, they can enter
torpor Torpor is a state of decreased physiological activity in an animal, usually marked by a reduced body temperature and metabolic rate. Torpor enables animals to survive periods of reduced food availability. The term "torpor" can refer to the time ...
, a state similar to
hibernation Hibernation is a state of minimal activity and metabolic depression undergone by some animal species. Hibernation is a seasonal heterothermy characterized by low body-temperature, slow breathing and heart-rate, and low metabolic rate. It mo ...
, and slow their metabolic rate to 1/15 of its normal rate.


Taxonomy and systematics

The family Trochilidae was introduced in 1825 by Irish zoologist
Nicholas Aylward Vigors Nicholas Aylward Vigors (1785 – 26 October 1840) was an Irish zoologist and politician. He popularized the classification of birds on the basis of the quinarian system. Early life Vigors was born at Old Leighlin, County Carlow on 1785 as fi ...
with '' Trochilus'' as the
type genus In biological taxonomy, the type genus is the genus which defines a biological family and the root of the family name. Zoological nomenclature According to the International Code of Zoological Nomenclature, "The name-bearing type of a nominal ...
.
Molecular phylogenetic Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...
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 In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end subfamily botanical names with "-oideae", and zool ...
.
Molecular phylogenetic Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...
studies determined the relationships between the major groups of hummingbirds. In the
cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...
below, the English names are those introduced in 1997. The Latin names are those introduced in 2013. In traditional
taxonomy Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...
, hummingbirds are placed in the order
Apodiformes Traditionally, the bird order Apodiformes contained three living families: the swifts (Apodidae), the treeswifts (Hemiprocnidae), and the hummingbirds (Trochilidae). In the Sibley-Ahlquist taxonomy, this order is raised to a superorder Apodi ...
, which also contains the
swift Swift or SWIFT most commonly refers to: * SWIFT, an international organization facilitating transactions between banks ** SWIFT code * Swift (programming language) * Swift (bird), a family of birds It may also refer to: Organizations * SWIFT ...
s, but some taxonomists have separated them into their own order, the Trochiliformes. Hummingbirds' wing
bone A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, an ...
s are hollow and fragile, making
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
ization 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 360 hummingbirds have been described. They have been traditionally divided into two
subfamilies In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end subfamily botanical names with "-oideae", and zool ...
: 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 In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic grou ...
. The hummingbirds form nine major
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
s: the topazes and
jacobins , logo = JacobinVignette03.jpg , logo_size = 180px , logo_caption = Seal of the Jacobin Club (1792–1794) , motto = "Live free or die"(french: Vivre libre ou mourir) , successor = P ...
, the hermits, the mangoes, the coquettes, the brilliants, the
giant hummingbird The giant hummingbird (''Patagona gigas'') is the only member of the genus ''Patagona'' and the largest member of the hummingbird family, weighing and having a wingspan of approximately and length of . This is approximately the same length as ...
(''Patagona gigas''), the mountaingems, the
bees Bees are winged insects closely related to wasps and ants, known for their roles in pollination and, in the case of the best-known bee species, the western honey bee, for producing honey. Bees are a monophyly, monophyletic lineage within the ...
, and the
emeralds Emerald is a gemstone and a variety of the mineral beryl (Be3Al2(SiO3)6) colored green by trace amounts of chromium or sometimes vanadium.Hurlbut, Cornelius S. Jr. and Kammerling, Robert C. (1991) ''Gemology'', John Wiley & Sons, New York, p. ...
. 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
tanager The tanagers (singular ) comprise the bird family Thraupidae, in the order Passeriformes. The family has a Neotropical distribution and is the second-largest family of birds. It represents about 4% of all avian species and 12% of the Neotrop ...
s).
Fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
hummingbirds are known from the
Pleistocene The Pleistocene ( , often referred to as the '' Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed i ...
of
Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
and the
Bahamas The Bahamas (), officially the Commonwealth of The Bahamas, is an island country within the Lucayan Archipelago of the West Indies in the North Atlantic. It takes up 97% of the Lucayan Archipelago's land area and is home to 88% of the ar ...
, 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 Gerald Mayr is a German palaeontologist who is Curator of Ornithology at the Senckenberg Research Institute in Frankfurt am Main, Hesse. He has published extensively on fossil birds, especially the Paleogene avifauna of Europe. He is an expert on ...
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 A museum ( ; plural museums or, rarely, musea) is a building or institution that Preservation (library and archival science), cares for and displays a collection (artwork), collection of artifacts and other objects of artistic, culture, cultu ...
drawer in
Stuttgart Stuttgart (; Swabian: ; ) is the capital and largest city of the German state of Baden-Württemberg. It is located on the Neckar river in a fertile valley known as the ''Stuttgarter Kessel'' (Stuttgart Cauldron) and lies an hour from the S ...
; they had been unearthed in a clay pit at
Wiesloch Wiesloch (, locally ; South Franconian: ''Wissloch''), is a town in northern Baden-Württemberg, Germany. It is situated 13 kilometres south of Heidelberg. After Weinheim, Sinsheim and Leimen it is the fourth largest town in the Rhein-Neckar-K ...
–Frauenweiler, south of
Heidelberg Heidelberg (; Palatine German: ') is a city in the German state of Baden-Württemberg, situated on the river Neckar in south-west Germany. As of the 2016 census, its population was 159,914, of which roughly a quarter consisted of students ...
,
Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwee ...
, 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 The Messel pit (german: Grube Messel) is a disused quarry near the village of Messel (Landkreis Darmstadt-Dieburg, Hesse) about southeast of Frankfurt am Main, Germany. Bituminous shale was mined there. Because of its abundance of well-preser ...
and in the
Caucasus The Caucasus () or Caucasia (), is a region between the Black Sea and the Caspian Sea, mainly comprising Armenia, Azerbaijan, Georgia, and parts of Southern Russia. The Caucasus Mountains, including the Greater Caucasus range, have historicall ...
, 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 Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologi ...
quite similar to that of the northern
Caribbean The Caribbean (, ) ( es, El Caribe; french: la Caraïbe; ht, Karayib; nl, De Caraïben) is a region of the Americas that consists of the Caribbean Sea, its islands (some surrounded by the Caribbean Sea and some bordering both the Caribbean Se ...
or southernmost
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...
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
adaptation In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the p ...
s, the decrease in size, and the dispersal to the Americas and extinction in
Eurasia Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelago ...
all occurred during this timespan.
DNA–DNA hybridization In genomics, DNA–DNA hybridization is a molecular biology technique that measures the degree of genetic similarity between pools of DNA sequences. It is usually used to determine the genetic distance between two organisms and has been used ...
results suggest that the main radiation of South American hummingbirds took place at least partly in the
Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recent ...
, some 12 to 13 million years ago, during the uplifting of the northern
Andes The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S l ...
. In 2013, a 50-million-year-old bird fossil unearthed in
Wyoming Wyoming () is a state in the Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the southwest, and Colorado to t ...
was found to be a predecessor to both hummingbirds and swifts before the groups diverged.


Evolution

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 known species of hummingbird are known from the early
Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but t ...
(
Rupelian The Rupelian is, in the geologic timescale, the older of two ages or the lower of two stages of the Oligocene Epoch/Series. It spans the time between . It is preceded by the Priabonian Stage (part of the Eocene) and is followed by the Chat ...
~34–28 million years ago) of Europe, belonging to the genus '' Eurotrochilus,'' which is very similar in its 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 treereconstructed from analysis of 284 of the world's 338 known
species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate ...
shows rapid diversification from 22 million years ago. Hummingbirds fall into nine main
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
s – the topazes, hermits, mangoes, brilliants, coquettes, the
giant hummingbird The giant hummingbird (''Patagona gigas'') is the only member of the genus ''Patagona'' and the largest member of the hummingbird family, weighing and having a wingspan of approximately and length of . This is approximately the same length as ...
, mountaingems,
bees Bees are winged insects closely related to wasps and ants, known for their roles in pollination and, in the case of the best-known bee species, the western honey bee, for producing honey. Bees are a monophyly, monophyletic lineage within the ...
, and
emeralds Emerald is a gemstone and a variety of the mineral beryl (Be3Al2(SiO3)6) colored green by trace amounts of chromium or sometimes vanadium.Hurlbut, Cornelius S. Jr. and Kammerling, Robert C. (1991) ''Gemology'', John Wiley & Sons, New York, p. ...
– defining their relationship to
nectar Nectar is a sugar-rich liquid produced by plants in glands called nectaries or nectarines, either within the flowers with which it attracts pollinating animals, or by extrafloral nectaries, which provide a nutrient source to animal mutualist ...
-bearing
flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek language, Greek words ('container, vessel') and ('seed'), and refers to ...
s and the birds' continued spread into new geographic areas. 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
evolution Evolution is change in the heredity, heritable Phenotypic trait, characteristics of biological populations over successive generations. These characteristics are the Gene expression, expressions of genes, which are passed on from parent to ...
ary pattern, as many as 140 hummingbird species can coexist in a specific region, such as the
Andes The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S l ...
range Range may refer to: Geography * Range (geographic), a chain of hills or mountains; a somewhat linear, complex mountainous or hilly area (cordillera, sierra) ** Mountain range, a group of mountains bordered by lowlands * Range, a term used to ...
. The hummingbird
evolutionary tree A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological sp ...
shows one key evolutionary factor appears to have been an altered taste receptor that enabled hummingbirds to seek nectar. 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 An evolutionary radiation is an increase in taxonomic diversity that is caused by elevated rates of speciation, that may or may not be associated with an increase in morphological disparity. Radiations may affect one clade or many, and be rapid ...
. Within the same geographic region, hummingbird clades co-evolved with nectar-bearing plant clades, affecting mechanisms of
pollination Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind. Pollinating agents can be animals such as insects, birds, ...
. 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'').


Sexual dimorphisms

Hummingbirds exhibit sexual size dimorphism according to
Rensch's rule Rensch's rule is a biological rule on allometrics, concerning the relationship between the extent of sexual size dimorphism and which sex is larger. Across species within a lineage, size dimorphism increases with increasing body size when the m ...
, 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 Mellisugini is one of the three tribes that make up the subfamily Trochilinae in the hummingbird family Trochilidae. The other two tribes in the subfamily are Lampornithini (mountain gems) and Trochilini (emeralds). The informal name "bees" ...
clade (bees) exhibits a large size dimorphism, with females being larger than males. Conversely, the
Lesbiini Lesbiini is one of the two tribes that make up the subfamily Lesbiinae in the hummingbird family Trochilidae. The other tribe is Heliantheini (brilliants). The informal name "coquettes" has been proposed for this group as the largest genus, ' ...
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 Forage is a plant material (mainly plant leaves and stems) eaten by grazing livestock. Historically, the term ''forage'' has meant only plants eaten by the animals directly as pasture, crop residue, or immature cereal crops, but it is also use ...
competitively and participate more frequently in courtship. Thus,
sexual selection Sexual selection is a mode of natural selection in which members of one biological sex choose mates of the other sex to mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex ( ...
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 Intraspecific competition is an interaction in population ecology, whereby members of the same species compete for limited resources. This leads to a reduction in fitness for both individuals, but the more fit individual survives and is able to ...
. 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.


Co-evolution with ornithophilous flowers

Hummingbirds are specialized
nectarivore In zoology, a nectarivore is an animal which derives its energy and nutrient requirements from a diet consisting mainly or exclusively of the sugar-rich nectar produced by flowering plants. Nectar as a food source presents a number of benefi ...
s and are 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, for example corolla length, curvature, and volume. Some species, especially those with unusual bill shapes, such as the sword-billed hummingbird and the sicklebills, are co-evolved 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 Dwarfism is a condition wherein an organism is exceptionally small, and mostly occurs in the animal kingdom. In humans, it is sometimes defined as an adult height of less than , regardless of sex; the average adult height among people with dw ...
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
wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tr ...
s into the near-ultraviolet, but hummingbird-pollinated flowers do not reflect these wavelengths as many insect-pollinated flowers do. This narrow
color spectrum The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called '' visible light'' or simply light. A typical human eye will respond to ...
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 Sucrose, a disaccharide, is a sugar composed of glucose and fructose subunits. It is produced naturally in plants and is the main constituent of white sugar. It has the molecular formula . For human consumption, sucrose is extracted and refi ...
, whereas insect-pollinated flowers typically produce more concentrated nectars dominated by
fructose Fructose, or fruit sugar, is a ketonic simple sugar found in many plants, where it is often bonded to glucose to form the disaccharide sucrose. It is one of the three dietary monosaccharides, along with glucose and galactose, that are absorb ...
and
glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, u ...
. Hummingbirds and the plants they visit for nectar have a tight co-evolutionary 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.


Bill evolution

Upon maturity, males of a particular species, ''Phaethornis longirostris,'' the
long-billed hermit The long-billed hermit (''Phaethornis longirostris'') is a bird in the family Trochilidae, the hummingbirds. It is found from central Mexico south through Central America, Colombia and Ecuador into Peru. Taxonomy and systematics It has of ...
, appear to be evolving a
dagger A dagger is a fighting knife with a very sharp point and usually two sharp edges, typically designed or capable of being used as a thrusting or stabbing weapon.State v. Martin, 633 S.W.2d 80 (Mo. 1982): This is the dictionary or popular-use de ...
-like weapon on the
beak The beak, bill, or rostrum is an external anatomical structure found mostly in birds, but also in turtles, non-avian dinosaurs and a few mammals. A beak is used for eating, preening, manipulating objects, killing prey, fighting, probing for foo ...
tip as a secondary sexual trait to defend mating areas.


Specialized characteristics and metabolism


Humming

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 force In fluid mechanics, an aerodynamic force is a force exerted on a body by the air (or other gas) in which the body is immersed, and is due to the relative motion between the body and the gas. Force There are two causes of aerodynamic force: * ...
s 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 A musical instrument is a device created or adapted to make musical sounds. In principle, any object that produces sound can be considered a musical instrument—it is through purpose that the object becomes a musical instrument. A person who pl ...
. The humming sound of hummingbirds is unique among flying animals, compared to the whine of
mosquito Mosquitoes (or mosquitos) are members of a group of almost 3,600 species of small flies within the family Culicidae (from the Latin ''culex'' meaning " gnat"). The word "mosquito" (formed by ''mosca'' and diminutive ''-ito'') is Spanish for "lit ...
es, buzz of
bee Bees are winged insects closely related to wasps and ants, known for their roles in pollination and, in the case of the best-known bee species, the western honey bee, for producing honey. Bees are a monophyletic lineage within the superfa ...
s, 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 pectoralis major () is a thick, fan-shaped or triangular convergent muscle, situated at the chest of the human body. It makes up the bulk of the chest muscles and lies under the breast. Beneath the pectoralis major is the pectoralis minor, ...
(the main downstroke muscle) and supracoracoideus (the main upstroke muscle).


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 Wind tunnels are large tubes with air blowing through them which are used to replicate the interaction between air and an object flying through the air or moving along the ground. Researchers use wind tunnels to learn more about how an aircraft ...
, 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 The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period). The amplitude of a non-periodic signal is its magnitude compared with a reference value. There are various definitions of am ...
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 The surface area of a solid object is a measure of the total area that the surface of the object occupies. The mathematical definition of surface area in the presence of curved surfaces is considerably more involved than the definition of ar ...
of their tail feathers into the shape of a fan. While hovering, the
visual system The visual system comprises the sensory organ (the eye) and parts of the central nervous system (the retina containing photoreceptor cells, the optic nerve, the optic tract and the visual cortex) which gives organisms the sense of sigh ...
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.


Vision

Although hummingbird eyes are small in diameter (5–6 mm), they are accommodated in the skull by reduced skull
ossification Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by cells named osteoblasts. It is synonymous with bone tissue formation. There are two processes resulting in th ...
, and occupy a relatively larger proportion of the skull compared to other birds and animals. Further, hummingbird eyes have relatively large
cornea The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical po ...
s, which comprise about 50% of the total transverse eye diameter, combined with an extraordinary density of
retinal ganglion cell A retinal ganglion cell (RGC) is a type of neuron located near the inner surface (the ganglion cell layer) of the retina of the eye. It receives visual information from photoreceptors via two intermediate neuron types: bipolar cells and re ...
s responsible for visual processing, containing some 45,000
neuron A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozo ...
s per mm2. The enlarged cornea relative to total eye diameter serves to increase the amount of light perception by the eye when the
pupil The pupil is a black hole located in the center of the iris of the eye that allows light to strike the retina.Cassin, B. and Solomon, S. (1990) ''Dictionary of Eye Terminology''. Gainesville, Florida: Triad Publishing Company. It appears black ...
is dilated maximally, enabling
nocturnal Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sen ...
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 physics and geosciences, the term spatial resolution refers to distance between independent measurements, or the physical dimension that represents a pixel of the image. While in some instruments, like cameras and telescopes, spatial resoluti ...
in the lateral and frontal
visual field The visual field is the "spatial array of visual sensations available to observation in introspectionist psychological experiments". Or simply, visual field can be defined as the entire area that can be seen when an eye is fixed straight at a poin ...
s. Morphological studies of the hummingbird brain showed that
neuron A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozo ...
al
hypertrophy Hypertrophy is the increase in the volume of an organ or tissue due to the enlargement of its component cells. It is distinguished from hyperplasia, in which the cells remain approximately the same size but increase in number.Updated by Linda J. ...
relatively the largest in any bird exists in a region called the pretectal nucleus lentiformis mesencephali (called the ''nucleus of the
optic tract In neuroanatomy, the optic tract () is a part of the visual system in the brain. It is a continuation of the optic nerve that relays information from the optic chiasm to the ipsilateral lateral geniculate nucleus (LGN), pretectal nuclei, and ...
'' 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 which hummingbirds encounter 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 Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30  PHz) to 400 nm (750  THz), shorter than that of visible light, but longer than X-rays. UV radiatio ...
and enables discrimination of non-spectral colors, possibly having a role in 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 The lentiform nucleus, or lenticular nucleus, comprises the putamen and the globus pallidus within the basal ganglia. With the caudate nucleus, it forms the dorsal striatum. It is a large, lens-shaped mass of gray matter just lateral to the i ...
which is tuned to fast-pattern velocities, enabling highly-tuned control and collision avoidance during forward flight.


Metabolism

With the exception of insects, hummingbirds while in flight have the highest
metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run ...
of all animals – a necessity to support the rapid beating of their wings during hovering and fast forward flight. Their heart rate can reach as high as 1,260 beats per minute (bpm), a rate once measured in a blue-throated hummingbird, with a breathing rate of 250 bpm, even at rest. During flight, oxygen consumption per gram of muscle tissue in a hummingbird is about 10 times higher than that measured in elite human athletes. 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 high enough to satisfy their extreme metabolic demands. A 2017 review indicated that hummingbirds have in their flight muscles a mechanism for "direct oxidation" of sugars into maximal ATP yield to support their high metabolic rate for hovering, foraging at altitude, and migrating. By relying on newly ingested sugars to fuel flight, hummingbirds can reserve their limited fat stores to sustain their overnight
fasting Fasting is the abstention from eating and sometimes drinking. From a purely physiological context, "fasting" may refer to the metabolic status of a person who has not eaten overnight (see " Breakfast"), or to the metabolic state achieved after co ...
or to power migratory flights. Studies of hummingbird metabolism address how a migrating ruby-throated hummingbird can cross of the
Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United St ...
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.


Hemoglobin adaptation to altitude

Dozens of hummingbird species live year-round in tropical mountain habitats at high altitudes, such as in the
Andes The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S l ...
over ranges of to where the oxygen content of 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 Hemoglobin (haemoglobin BrE) (from the Greek word αἷμα, ''haîma'' 'blood' + Latin ''globus'' 'ball, sphere' + ''-in'') (), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein present in red blood cells (erythrocyt ...
had increased oxygen- binding affinity, and that this adaptive effect likely resulted from evolutionary
mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, ...
s within the hemoglobin molecule via specific amino acid changes due to
natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations. Char ...
.


Heat dissipation

The high metabolic rate of hummingbirds – especially during rapid forward flight and hovering – produces increased body heat that requires specialized mechanisms of
thermoregulation Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature ...
for heat dissipation, which becomes an even greater challenge in hot, humid climates. Hummingbirds dissipate heat partially by
evaporation Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. High concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when h ...
through exhaled air, and from body structures with thin or no feather covering, such as around the eyes, shoulders, under the wings (
patagia The patagium (plural: patagia) is a membranous body part that assists an animal in obtaining lift when gliding or flight. The structure is found in extant and extinct groups of flying and gliding animals including bats, birds, some dromaeosa ...
), 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 , 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 Exhalation (or expiration) is the flow of the breath out of an organism. In animals, it is the movement of air from the lungs out of the airways, to the external environment during breathing. This happens due to elastic properties of the lung ...
. In cold climates, hummingbirds retract their feet into breast feathers to eliminate skin exposure and minimize heat dissipation.


Kidney function

The dynamic range of metabolic rates in hummingbirds requires a parallel dynamic range in
kidney The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; blo ...
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
electrolyte An electrolyte is a medium containing ions that is electrically conducting through the movement of those ions, but not conducting electrons. This includes most soluble salts, acids, and bases dissolved in a polar solvent, such as water. Upon ...
s after consuming nectars with high amounts of
sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...
and
chloride The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride salts ...
or none, indicating that kidney and glomerular structures must be highly specialized for variations in nectar
mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ...
quality. Morphological studies on
Anna's hummingbird Anna's hummingbird (''Calypte anna'') is a medium-sized bird species of the family Trochilidae. It was named after Anna Masséna, Duchess of Rivoli. It is native to western coastal regions of North America. In the early 20th century, Anna's hu ...
kidneys showed adaptations of high
capillary A capillary is a small blood vessel from 5 to 10 micrometres (μm) in diameter. Capillaries are composed of only the tunica intima, consisting of a thin wall of simple squamous endothelial cells. They are the smallest blood vessels in the body ...
density in close proximity to
nephron The nephron is the minute or microscopic structural and functional unit of the kidney. It is composed of a renal corpuscle and a renal tubule. The renal corpuscle consists of a tuft of capillaries called a glomerulus and a cup-shaped structure ...
s, allowing for precise regulation of water and electrolytes.


Song and vocal learning

Consisting of chirps, squeaks, whistles and buzzes, hummingbird songs originate from at least seven specialized nuclei in the
forebrain In the anatomy of the brain of vertebrates, the forebrain or prosencephalon is the rostral (forward-most) portion of the brain. The forebrain (prosencephalon), the midbrain (mesencephalon), and hindbrain (rhombencephalon) are the three primar ...
. 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 (
parrot Parrots, also known as psittacines (), are birds of the roughly 398 species in 92 genera comprising the order Psittaciformes (), found mostly in tropical and subtropical regions. The order is subdivided into three superfamilies: the Psittac ...
s and
songbird A songbird is a bird belonging to the suborder Passeri of the perching birds (Passeriformes). Another name that is sometimes seen as the scientific or vernacular name is Oscines, from Latin ''oscen'', "songbird". The Passeriformes contains 500 ...
s) and a few groups of mammals (including humans, whales and dolphins, and
bat Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most bi ...
s). 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 In biology, epigenetics is the study of stable phenotypic changes (known as ''marks'') that do not involve alterations in the DNA sequence. The Greek prefix '' epi-'' ( "over, outside of, around") in ''epigenetics'' implies features that are " ...
constraints possibly derived from a common ancestor. 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 Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it. This limit varies f ...
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. The avian vocal organ, the
syrinx In classical Greek mythology, Syrinx (Greek Σύριγξ) was a nymph and a follower of Artemis, known for her chastity. Pursued by the amorous god Pan, she ran to a river's edge and asked for assistance from the river nymphs. In answer, s ...
, plays an important role in understanding hummingbird song production. What makes the hummingbird's syrinx different from that of other birds in the
Apodiformes Traditionally, the bird order Apodiformes contained three living families: the swifts (Apodidae), the treeswifts (Hemiprocnidae), and the hummingbirds (Trochilidae). In the Sibley-Ahlquist taxonomy, this order is raised to a superorder Apodi ...
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.


Torpor

The metabolism of hummingbirds can slow at night or at any time when food is not readily available; the birds enter a hibernatory, deep-sleep state (known as
torpor Torpor is a state of decreased physiological activity in an animal, usually marked by a reduced body temperature and metabolic rate. Torpor enables animals to survive periods of reduced food availability. The term "torpor" can refer to the time ...
) 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 Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature ...
in a
Caribbean The Caribbean (, ) ( es, El Caribe; french: la Caraïbe; ht, Karayib; nl, De Caraïben) is a region of the Americas that consists of the Caribbean Sea, its islands (some surrounded by the Caribbean Sea and some bordering both the Caribbean Se ...
hummingbird was shown to fall from 40 to 18 °C, with
heart The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxid ...
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 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 In physiology, dehydration is a lack of total body water, with an accompanying disruption of metabolic processes. It occurs when free water loss exceeds free water intake, usually due to exercise, disease, or high environmental temperature. Mi ...
, the
kidney function Assessment of kidney function occurs in different ways, using the presence of symptoms and signs, as well as measurements using urine tests, blood tests, and medical imaging. Functions of a healthy kidney include maintaining a person's fluid ...
declines, preserving needed compounds, such as
glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, u ...
, water, and nutrients. The circulating
hormone A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are required ...
, 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 Photoperiodism is the physiological reaction of organisms to the length of night or a dark period. It occurs in plants and animals. Plant photoperiodism can also be defined as the developmental responses of plants to the relative lengths of light ...
and duration of torpor.


Lifespan

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
shrew Shrews ( family Soricidae) are small mole-like mammals classified in the order Eulipotyphla. True shrews are not to be confused with treeshrews, otter shrews, elephant shrews, West Indies shrews, or marsupial shrews, which belong to different ...
s, 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.Patuxent Wildlife Research Center, Bird Banding Laboratory
Longevity Records AOU Numbers 3930–4920
2009-08-31. Retrieved 2009-09-27.


Predators

Praying mantises have been observed as predators of hummingbirds. Other predators include
dragonflies A dragonfly is a flying insect belonging to the infraorder Anisoptera below the order Odonata. About 3,000 extant species of true dragonfly are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat thre ...
,
frog A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-frog" ''Triadobatrachus'' is ...
s,
orb-weaver spider Orb-weaver spiders are members of the spider family Araneidae. They are the most common group of builders of spiral wheel-shaped webs often found in gardens, fields, and forests. The English word "orb" can mean "circular", hence the English na ...
s, and other birds, such as the roadrunner.


Reproduction

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 A walnut is the edible seed of a drupe of any tree of the genus '' Juglans'' (family Juglandaceae), particularly the Persian or English walnut, '' Juglans regia''. Although culinarily considered a "nut" and used as such, it is not a tru ...
shell to several centimeters in diameter. Many hummingbird species use
spider silk Spider silk is a protein fibre spun by spiders. Spiders use their silk to make webs or other structures, which function as sticky nets to catch other animals, or as nests or cocoons to protect their offspring, or to wrap up prey. They ca ...
and
lichen A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship. The unique properties of the silk allow the nest to expand as the young hummingbirds grow.Archived a
Ghostarchive
and th
Wayback Machine
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
arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chitin, o ...
s and nectar by inserting her bill into the open mouth of a
nestling Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight ...
, 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.


Feather colors

To serve courtship and territorial
competition Competition is a rivalry where two or more parties strive for a common goal which cannot be shared: where one's gain is the other's loss (an example of which is a zero-sum game). Competition can arise between entities such as organisms, indivi ...
, many male hummingbirds have
plumage Plumage ( "feather") is a layer of feathers that covers a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage differ between species and subspecies and may vary with age classes. Within species, ...
with bright, varied coloration resulting both from
pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compou ...
ation in the feathers and from
prism Prism usually refers to: * Prism (optics), a transparent optical component with flat surfaces that refract light * Prism (geometry), a kind of polyhedron Prism may also refer to: Science and mathematics * Prism (geology), a type of sedimentar ...
al cells within the top layers of feathers of the head,
gorget A gorget , from the French ' meaning throat, was a band of linen wrapped around a woman's neck and head in the medieval period or the lower part of a simple chaperon hood. The term later described a steel or leather collar to protect the thr ...
, breast, back and wings. When
sunlight Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when th ...
hits these cells, it is split into
wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tr ...
s that reflect to the observer in varying degrees of intensity, with the feather structure acting as a
diffraction grating In optics, a diffraction grating is an optical component with a periodic structure that diffracts light into several beams travelling in different directions (i.e., different diffraction angles). The emerging coloration is a form of structura ...
.
Iridescent Iridescence (also known as goniochromism) is the phenomenon of certain surfaces that appear to gradually change color as the angle of view or the angle of illumination changes. Examples of iridescence include soap bubbles, feathers, butterfl ...
hummingbird colors result from a combination of refraction and pigmentation, since the diffraction structures themselves are made of
melanin Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amino ...
, a pigment, and may also be colored by
carotenoid Carotenoids (), also called tetraterpenoids, are yellow, orange, and red organic pigments that are produced by plants and algae, as well as several bacteria, and fungi. Carotenoids give the characteristic color to pumpkins, carrots, parsnips, ...
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 Anna's hummingbird (''Calypte anna'') is a medium-sized bird species of the family Trochilidae. It was named after Anna Masséna, Duchess of Rivoli. It is native to western coastal regions of North America. In the early 20th century, Anna's hu ...
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 A crown is a traditional form of head adornment, or hat, worn by monarchs as a symbol of their power and dignity. A crown is often, by extension, a symbol of the monarch's government or items endorsed by it. The word itself is used, partic ...
feathers than those fed a low-protein diet. Additionally, birds on a high-protein diet grew yellower (higher
hue In color theory, hue is one of the main properties (called color appearance parameters) of a color, defined technically in the CIECAM02 model as "the degree to which a stimulus can be described as similar to or different from stimuli that ...
) green tail feathers than birds on a low-protein diet.


Aerodynamics of flight

Hummingbird flight has been studied intensively from an
aerodynamic Aerodynamics, from grc, ἀήρ ''aero'' (air) + grc, δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dyn ...
perspective using wind tunnels and high-speed
video camera A video camera is an optical instrument that captures videos (as opposed to a movie camera, which records images on film). Video cameras were initially developed for the television industry but have since become widely used for a variety of othe ...
s. Two studies of
rufous Rufous () is a color that may be described as reddish- brown or brownish-red, as of rust or oxidised iron. The first recorded use of ''rufous'' as a color name in English was in 1782. However, the color is also recorded earlier in 1527 as a ...
or
Anna's hummingbird Anna's hummingbird (''Calypte anna'') is a medium-sized bird species of the family Trochilidae. It was named after Anna Masséna, Duchess of Rivoli. It is native to western coastal regions of North America. In the early 20th century, Anna's hu ...
s 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 Lift or LIFT may refer to: Physical devices * Elevator, or lift, a device used for raising and lowering people or goods ** Paternoster lift, a type of lift using a continuous chain of cars which do not stop ** Patient lift, or Hoyer lift, mobile ...
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 The Sphingidae are a family of moths (Lepidoptera) called sphinx moths, also colloquially known as hawk moths, with many of their caterpillars known as “hornworms”; it includes about 1,450 species. It is best represented in the tropics, but ...
. Further studies using
electromyography Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG is performed using an instrument called an electromyograph to produce a record called an electromyogram. An electromyog ...
in hovering rufous hummingbirds showed that
muscle strain A strain is an acute or chronic soft tissue injury that occurs to a muscle, tendon, or both. The equivalent injury to a ligament is a sprain. Generally, the muscle or tendon overstretches and partially tears, under more physical stress than i ...
in the
pectoralis major The pectoralis major () is a thick, fan-shaped or triangular convergent muscle, situated at the chest of the human body. It makes up the bulk of the chest muscles and lies under the breast. Beneath the pectoralis major is the pectoralis minor, ...
(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 alula , or bastard wing, (plural ''alulae'') is a small projection on the anterior edge of the wing of modern birds and a few non-avian dinosaurs. The word is Latin and means "winglet"; it is the diminutive of ''ala'', meaning "wing". The a ...
. 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.


Feather sonation


Courtship dives

When courting, the male Anna's hummingbird ascends some above a female, before diving at a speed of , equal to 385 body lengths/sec – producing a high-pitched sound near the female at the
nadir The nadir (, ; ar, نظير, naẓīr, counterpart) is the direction pointing directly ''below'' a particular location; that is, it is one of two vertical directions at a specified location, orthogonal to a horizontal flat surface. The dire ...
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 falcon The peregrine falcon (''Falco peregrinus''), also known as the peregrine, and historically as the duck hawk in North America, is a cosmopolitan bird of prey ( raptor) in the family Falconidae. A large, crow-sized falcon, it has a blue-grey ba ...
s in pursuit of prey. At maximum descent speed, about 10 g of
gravitational force In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the strong ...
occur in the courting hummingbird during a dive (Note:
G-force The gravitational force equivalent, or, more commonly, g-force, is a measurement of the type of force per unit mass – typically acceleration – that causes a perception of weight, with a g-force of 1 g (not gram in mass measure ...
is generated as the bird pulls out of the dive). By comparison to humans, this is a G-force acceleration well beyond the threshold of causing near loss of
consciousness Consciousness, at its simplest, is sentience and awareness of internal and external existence. However, the lack of definitions has led to millennia of analyses, explanations and debates by philosophers, theologians, linguisticians, and scien ...
in
fighter pilot A fighter pilot is a military aviator trained to engage in air-to-air combat, air-to-ground combat and sometimes electronic warfare while in the cockpit of a fighter aircraft. Fighter pilots undergo specialized training in aerial warfare and ...
s (occurring at about +5 Gz) during flight of fixed-wing aircraft in a high-speed
banked turn A banked turn (or banking turn) is a turn or change of direction in which the vehicle banks or inclines, usually towards the inside of the turn. For a road or railroad this is usually due to the roadbed having a transverse down-slope towards the ...
. 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 Aerodynamics, from grc, ἀήρ ''aero'' (air) + grc, δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dyn ...
of rapid air flow past tail feathers, causing them to flutter in a
vibration Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point. The word comes from Latin ''vibrationem'' ("shaking, brandishing"). The oscillations may be periodic, such as the motion of a pendulum—or random, suc ...
, 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 The rufous hummingbird (''Selasphorus rufus'') is a small hummingbird, about long with a long, straight and slender bill. These birds are known for their extraordinary flight skills, flying during their migratory transits. It is one of nine s ...
,
Allen's hummingbird Allen's hummingbird (''Selasphorus sasin'') is a species of hummingbird that breeds in the western United States. It is one of seven species in the genus ''Selasphorus''. Description Allen's hummingbird is a small bird, with mature adults reac ...
, and the streamertail species, as well as the tail of the
Costa's hummingbird Costa's hummingbird (''Calypte costae'') is a bird species in the hummingbird family Trochilidae. It breeds in the arid region of the southwest United States and northwest Mexico; it winters in western Mexico. Taxonomy Costa's hummingbird was ...
and the black-chinned hummingbird, and a number of related species. The
harmonic A harmonic is a wave with a frequency that is a positive integer multiple of the '' fundamental frequency'', the frequency of the original periodic signal, such as a sinusoidal wave. The original signal is also called the ''1st harmonic'', the ...
s of sounds during courtship dives vary across species of hummingbirds.


Wing feather trill

Male rufous and broad-tailed hummingbirds (genus ''
Selasphorus ''Selasphorus'' is a genus of hummingbirds from Middle and North America. Taxonomy The genus ''Selasphorus'' was introduced in 1832 by the English naturalist William John Swainson to accommodate the rufous hummingbird which is now the type spe ...
'') have a distinctive wing feature during normal flight that sounds like jingling or a buzzing shrill whistle. 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: * Announces the sex and presence of a male bird * Provides audible aggressive defense of a feeding territory and an intrusion tactic * Enhances communication of a threat * Favors mate attraction and courtship


Range

Hummingbirds are restricted to the Americas from south central
Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U. ...
to
Tierra del Fuego Tierra del Fuego (, ; Spanish for "Land of the Fire", rarely also Fireland in English) is an archipelago off the southernmost tip of the South American mainland, across the Strait of Magellan. The archipelago consists of the main island, Isla ...
, including the
Caribbean The Caribbean (, ) ( es, El Caribe; french: la Caraïbe; ht, Karayib; nl, De Caraïben) is a region of the Americas that consists of the Caribbean Sea, its islands (some surrounded by the Caribbean Sea and some bordering both the Caribbean Se ...
. The majority of species occur in tropical and subtropical Central and South America, but several species also breed in temperate climates and some
hillstar The hillstars are hummingbirds of the genus ''Oreotrochilus''. They are native to the Andes in South America. The '' Urochroa'' hillstars are not closely related. Species list Their genus contains seven species: * Ecuadorian hillstar (''Oreot ...
s occur even in alpine Andean highlands at altitudes up to . The greatest
species richness Species richness is the number of different species represented in an ecological community, landscape or region. Species richness is simply a count of species, and it does not take into account the abundances of the species or their relative a ...
is in humid tropical and subtropical forests of the northern Andes and adjacent foothills, but the number of species found in the
Atlantic Forest The Atlantic Forest ( pt, Mata Atlântica) is a South American forest that extends along the Atlantic coast of Brazil from Rio Grande do Norte state in the northeast to Rio Grande do Sul state in the south and inland as far as Paraguay and th ...
, Central America or southern
Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...
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 Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...
each, Colombia alone has more than 160 and the comparably small
Ecuador Ecuador ( ; ; Quechua: ''Ikwayur''; Shuar: ''Ecuador'' or ''Ekuatur''), officially the Republic of Ecuador ( es, República del Ecuador, which literally translates as "Republic of the Equator"; Quechua: ''Ikwadur Ripuwlika''; Shuar: ''Ekua ...
has about 130 species. The migratory ruby-throated hummingbird breeds in a range from the
Southeastern United States The Southeastern United States, also referred to as the American Southeast or simply the Southeast, is a geographical region of the United States. It is located broadly on the eastern portion of the southern United States and the southern por ...
to
Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central Ca ...
, 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 The rufous hummingbird (''Selasphorus rufus'') is a small hummingbird, about long with a long, straight and slender bill. These birds are known for their extraordinary flight skills, flying during their migratory transits. It is one of nine s ...
is the most widespread species in western North America,Williamson, S. L. (2002). ''A Field Guide to Hummingbirds of North America'' (Peterson Field Guide Series). Houghton Mifflin, Boston. and the only hummingbird to be recorded outside of the Americas, having occurred in the
Chukchi Peninsula The Chukchi Peninsula (also Chukotka Peninsula or Chukotski Peninsula; russian: Чуко́тский полуо́стров, ''Chukotskiy poluostrov'', short form russian: Чуко́тка, ''Chukotka''), at about 66° N 172° W, is the eastern ...
of Russia.


Migration

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 Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to th ...
, 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 South Texas is a region of the U.S. state of Texas that lies roughly south of—and includes—San Antonio. The southern and western boundary is the Rio Grande, and to the east it is the Gulf of Mexico. The population of this region is about 4.96 ...
. Ruby-throated hummingbirds are common along the Atlantic flyway, and migrate in summer from as far north as
Atlantic Canada Atlantic Canada, also called the Atlantic provinces (french: provinces de l'Atlantique), is the region of Eastern Canada comprising the provinces located on the Atlantic coast, excluding Quebec. The four provinces are New Brunswick, Newfoundlan ...
, returning to
Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...
, South America, southern Texas, and
Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to th ...
to winter. During winter in southern
Louisiana Louisiana , group=pronunciation (French: ''La Louisiane'') is a state in the Deep South and South Central regions of the United States. It is the 20th-smallest by area and the 25th most populous of the 50 U.S. states. Louisiana is border ...
, black-chinned, buff-bellied, calliope, Allen's, Anna's, ruby-throated, rufous, broad-tailed, and broad-billed hummingbirds are present. The
rufous hummingbird The rufous hummingbird (''Selasphorus rufus'') is a small hummingbird, about long with a long, straight and slender bill. These birds are known for their extraordinary flight skills, flying during their migratory transits. It is one of nine s ...
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 The Gulf of Mexico ( es, Golfo de México) is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United St ...
and Florida, rather than in western or central Mexico. By migrating in spring as far north as the
Yukon Yukon (; ; formerly called Yukon Territory and also referred to as the Yukon) is the smallest and westernmost of Canada's three territories. It also is the second-least populated province or territory in Canada, with a population of 43,964 as ...
or southern
Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U. ...
, 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 Displacement may refer to: Physical sciences Mathematics and Physics *Displacement (geometry), is the difference between the final and initial position of a point trajectory (for instance, the center of mass of a moving object). The actual path ...
of body size, the rufous hummingbird makes perhaps the longest migratory journey of any bird in the world. At just over 3 in long, rufous hummingbirds travel 3,900 miles one-way from Alaska to Mexico in late summer, a distance equal to 78,470,000 body lengths. By comparison, the 13-inch-long
Arctic tern The Arctic tern (''Sterna paradisaea'') is a tern in the family (biology), family Laridae. This bird has a :wiktionary:circumpolar, circumpolar breeding distribution covering the Arctic and sub-Arctic regions of Europe (as far south as Brittan ...
makes a one-way flight of about 11,185 miles, 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 The Pacific Flyway is a major north-south flyway for migratory birds in the Americas, extending from Alaska to Patagonia. Every year, migratory birds travel some or all of this distance both in spring and in fall, following food sources, heading ...
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.


Diet and specializations for food gathering

For
nutrition Nutrition is the biochemical and physiological process by which an organism uses food to support its life. It provides organisms with nutrients, which can be metabolized to create energy and chemical structures. Failure to obtain sufficient nu ...
, hummingbirds eat a variety of insects, including
mosquito Mosquitoes (or mosquitos) are members of a group of almost 3,600 species of small flies within the family Culicidae (from the Latin ''culex'' meaning " gnat"). The word "mosquito" (formed by ''mosca'' and diminutive ''-ito'') is Spanish for "lit ...
es,
fruit flies Fruit fly may refer to: Organisms * Drosophilidae, a family of small flies, including: ** ''Drosophila'', the genus of small fruit flies and vinegar flies ** ''Drosophila melanogaster'' or common fruit fly ** '' Drosophila suzukii'' or Asian fruit ...
,
gnat A gnat () is any of many species of tiny flying insects in the dipterid suborder Nematocera, especially those in the families Mycetophilidae, Anisopodidae and Sciaridae. They can be both biting and non-biting. Most often they fly in large num ...
s in flight, or
aphid Aphids are small sap-sucking insects and members of the superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white woolly aphids. A t ...
s on leaves and
spider Spiders ( order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species div ...
s in their webs. The lower
beak The beak, bill, or rostrum is an external anatomical structure found mostly in birds, but also in turtles, non-avian dinosaurs and a few mammals. A beak is used for eating, preening, manipulating objects, killing prey, fighting, probing for foo ...
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
swarm Swarm behaviour, or swarming, is a collective behaviour exhibited by entities, particularly animals, of similar size which aggregate together, perhaps milling about the same spot or perhaps moving ''en masse'' or migrating in some direction. ...
s in a method called "hover-
hawking Hawking may refer to: People * Stephen Hawking (1942–2018), English theoretical physicist and cosmologist * Hawking (surname), a family name (including a list of other persons with the name) Film * ''Hawking'' (2004 film), about Stephen Ha ...
" 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
nutrient A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excrete ...
s, 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 10–15% of their time feeding and 75–80% sitting and digesting. Because their high metabolism makes them vulnerable to
starvation Starvation is a severe deficiency in caloric energy intake, below the level needed to maintain an organism's life. It is the most extreme form of malnutrition. In humans, prolonged starvation can cause permanent organ damage and eventually, ...
, 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 for itself. Additionally, hummingbirds have an enlarged
hippocampus The hippocampus (via Latin from Greek , 'seahorse') is a major component of the brain of humans and other vertebrates. Humans and other mammals have two hippocampi, one in each side of the brain. The hippocampus is part of the limbic system, a ...
, 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 Gesneriaceae, the gesneriad family, is a family of flowering plants consisting of about 152 genera and ca. 3,540 species in the tropics and subtropics of the Old World (almost all Didymocarpoideae) and the New World (most Gesnerioideae), wit ...
. The bill of the fiery-tailed awlbill has an upturned tip, as in the
avocet The four species of avocets are a genus, ''Recurvirostra'', of waders in the same avian family as the stilts. The genus name comes from Latin , 'curved backwards' and , 'bill'. The common name is thought to derive from the Italian ( Ferrarese) ...
s. The male tooth-billed hummingbird has barracuda-like spikes at the tip of its long, straight bill. The two halves of a hummingbird's bill have a pronounced overlap, with the lower half (
mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...
) fitting tightly inside the upper half (
maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...
). When a hummingbird feeds on nectar, the bill is usually opened only slightly, allowing the tongue to dart out and into the interior of flowers. 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 Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relative ...
downward to widen the
gape The beak, bill, or rostrum is an external anatomical structure found mostly in birds, but also in turtles, non-avian dinosaurs and a few mammals. A beak is used for eating, preening, manipulating objects, killing prey, fighting, probing for food, ...
for successful capture.


Perception of sweet nectar

Perception of sweetness in nectar evolved in hummingbirds during their
genetic divergence Genetic divergence is the process in which two or more populations of an ancestral species accumulate independent genetic changes (mutations) through time, often leading to reproductive isolation and continued mutation even after the populations hav ...
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 Umami ( from ja, 旨味 ), or savoriness, is one of the five basic tastes. It has been described as savory and is characteristic of broths and cooked meats. People taste umami through taste receptors that typically respond to glutamates and ...
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 In mathematics (and more specifically geometry), a semicircle is a one-dimensional locus of points that forms half of a circle. The full arc of a semicircle always measures 180° (equivalently, radians, or a half-turn). It has only one line ...
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
millisecond A millisecond (from ''milli-'' and second; symbol: ms) is a unit of time in the International System of Units (SI) equal to one thousandth (0.001 or 10−3 or 1/1000) of a second and to 1000 microseconds. A unit of 10 milliseconds may be called ...
s 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 and the nectar moves up the grooves, like a
pump A pump is a device that moves fluids (liquids or gases), or sometimes slurries, by mechanical action, typically converted from electrical energy into hydraulic energy. Pumps can be classified into three major groups according to the method they ...
action, with
capillary action Capillary action (sometimes called capillarity, capillary motion, capillary rise, capillary effect, or wicking) is the process of a liquid flowing in a narrow space without the assistance of, or even in opposition to, any external forces li ...
not involved. Consequently, tongue flexibility enables accessing, transporting and unloading nectar via pump action, not by a capillary
syphon A siphon (from grc, σίφων, síphōn, "pipe, tube", also spelled nonetymologically syphon) is any of a wide variety of devices that involve the flow of liquids through tubes. In a narrower sense, the word refers particularly to a tube in a ...
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 feeder A birdfeeder, bird table, or tray feeder are devices placed outdoors to supply bird food to birds (bird feeding). The success of a bird feeder in attracting birds depends upon its placement and the kinds of foods offered, as different species h ...
s, 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 Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind. Pollinating agents can be animals such as insects, birds, ...
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 Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in fr ...
, which can be harmful, and brown sugar,
agave syrup ''Agave'' (; ; ) is a genus of monocots native to the hot and arid regions of the Americas and the Caribbean, although some ''Agave'' species are also native to tropical areas of North America, such as Mexico. The genus is primarily known for i ...
,
molasses Molasses () is a viscous substance resulting from refining sugarcane or sugar beets into sugar. Molasses varies in the amount of sugar, method of extraction and age of the plant. Sugarcane molasses is primarily used to sweeten and flavour foods. ...
, and
artificial sweeteners A sugar substitute is a food additive that provides a sweetness like that of sugar while containing significantly less food energy than sugar-based sweeteners, making it a zero-calorie () or low-calorie sweetener. Artificial sweeteners may be d ...
also should not be used.
Honey Honey is a sweet and viscous substance made by several bees, the best-known of which are honey bees. Honey is made and stored to nourish bee colonies. Bees produce honey by gathering and then refining the sugary secretions of plants (primaril ...
is made by
bee Bees are winged insects closely related to wasps and ants, known for their roles in pollination and, in the case of the best-known bee species, the western honey bee, for producing honey. Bees are a monophyletic lineage within the superfa ...
s from the nectar of flowers, but it is not good to use in feeders because when it is diluted with water,
microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...
s 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
preservative A preservative is a substance or a chemical that is added to products such as food products, beverages, pharmaceutical drugs, paints, biological samples, cosmetics, wood, and many other products to prevent decomposition by microbial growth or by ...
s 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 "
beacon A beacon is an intentionally conspicuous device designed to attract attention to a specific location. A common example is the lighthouse, which draws attention to a fixed point that can be used to navigate around obstacles or into port. More mode ...
s" for foraging. Hummingbirds depend little on visual cues of flower color to beacon to nectar-rich locations, but rather they used 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 In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tr ...
for the bird's
visual system The visual system comprises the sensory organ (the eye) and parts of the central nervous system (the retina containing photoreceptor cells, the optic nerve, the optic tract and the visual cortex) which gives organisms the sense of sight (the ...
, 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 The visual system comprises the sensory organ (the eye) and parts of the central nervous system (the retina containing photoreceptor cells, the optic nerve, the optic tract and the visual cortex) which gives organisms the sense of sigh ...
having four single
cone cell Cone cells, or cones, are photoreceptor cells in the retinas of vertebrate eyes including the human eye. They respond differently to light of different wavelengths, and the combination of their responses is responsible for color vision. Cones ...
s and a double cone screened by photoreceptor
oil droplet Oil droplets are found in the eyes of some animals, being located in the photoreceptor cells. They are especially common in the eyes of diurnal (active during the day) reptiles (e.g. lizards, turtles) and birds (see bird vision), though are prese ...
s which enhance color discrimination.


Olfaction

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 Smell may refer to; * Odor, airborne molecules perceived as a scent or aroma * Sense of smell, the scent also known scientifically as olfaction * "Smells" (''Bottom''), an episode of ''Bottom'' * The Smell, a music venue in Los Angeles, Californ ...
the presence in nectar of insect defensive chemicals (such as
formic acid Formic acid (), systematically named methanoic acid, is the simplest carboxylic acid, and has the chemical formula HCOOH and structure . It is an important intermediate in chemical synthesis and occurs naturally, most notably in some ants. E ...
) and aggregation
pheromone A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavi ...
s of foraging ants, which discourage feeding.


Superficially similar species

Some species of
sunbird Sunbirds and spiderhunters make up the family Nectariniidae of passerine birds. They are small, slender passerines from the Old World, usually with downward-curved bills. Many are brightly coloured, often with iridescent feathers, particularly i ...
s of Africa, southern and southeastern Asia, and Australia resemble hummingbirds in appearance and behavior, as do perhaps also the
honeyeater The honeyeaters are a large and diverse family, Meliphagidae, of small to medium-sized birds. The family includes the Australian chats, myzomelas, friarbirds, wattlebirds, miners and melidectes. They are most common in Australia and New Guine ...
s of Australia and Pacific islands. These two groups, however, 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.


In myth and culture

*
Aztecs The Aztecs () were a Mesoamerican culture that flourished in central Mexico in the post-classic period from 1300 to 1521. The Aztec people included different ethnic groups of central Mexico, particularly those groups who spoke the Nahuatl l ...
wore hummingbird
talismans A talisman is any object ascribed with religious or magical powers intended to protect, heal, or harm individuals for whom they are made. Talismans are often portable objects carried on someone in a variety of ways, but can also be installed perm ...
, both artistic representations of hummingbirds and fetishes made from actual hummingbird parts: emblematic for their 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 War is an intense armed conflict between states, governments, societies, or paramilitary groups such as mercenaries, insurgents, and militias. It is generally characterized by extreme violence, destruction, and mortality, using regular o ...
to the wearer. * The Aztec god of war Huitzilopochtli is often depicted as a hummingbird. It was also believed that fallen warriors would return to earth as hummingbirds and butterflies. The
Nahuatl Nahuatl (; ), Aztec, or Mexicano is a language or, by some definitions, a group of languages of the Uto-Aztecan language family. Varieties of Nahuatl are spoken by about Nahua peoples, most of whom live mainly in Central Mexico and have smaller ...
word ''huitzil'' (hummingbird) is an
onomatopoeic Onomatopoeia is the process of creating a word that phonetically imitates, resembles, or suggests the sound that it describes. Such a word itself is also called an onomatopoeia. Common onomatopoeias include animal noises such as ''oink'', '' ...
word derived from the sounds of the hummingbird's wing-beats and zooming flight. * Likewise in part Mt. Umunhum in the
Santa Cruz Mountains The Santa Cruz Mountains, part of the Pacific Coast Ranges, are a mountain range in central and Northern California, United States. They form a ridge down the San Francisco Peninsula, south of San Francisco. They separate the Pacific Ocean from ...
in
Northern California Northern California (colloquially known as NorCal) is a geographic and cultural region that generally comprises the northern portion of the U.S. state of California. Spanning the state's northernmost 48 counties, its main population centers inc ...
is
Ohlone The Ohlone, formerly known as Costanoans (from Spanish meaning 'coast dweller'), are a Native American people of the Northern California coast. When Spanish explorers and missionaries arrived in the late 18th century, the Ohlone inhabited the ...
for "Resting Place of the Hummingbird" * One of the
Nazca Lines The Nazca Lines are a group of geoglyphs made in the soil of the Nazca Desert in southern Peru. They were created between 500 BCE and 500 CE by people making depressions or shallow incisions in the desert floor, removing pebbles and le ...
depicts a hummingbird (right). * The
Hopi The Hopi are a Native American ethnic group who primarily live on the Hopi Reservation in northeastern Arizona, United States. As of the 2010 census, there are 19,338 Hopi in the country. The Hopi Tribe is a sovereign nation within the United ...
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. *
Trinidad and Tobago Trinidad and Tobago (, ), officially the Republic of Trinidad and Tobago, is the southernmost island country in the Caribbean. Consisting of the main islands Trinidad and Tobago, and numerous much smaller islands, it is situated south of Gr ...
, known as "The land of the hummingbird," displays a hummingbird on that nation's coat of arms, 1-cent coin and emblem of its national airline,
Caribbean Airlines Caribbean Airlines Limited is the state-owned airline and flag carrier of Trinidad and Tobago. The airline is also the flag carrier of Jamaica and Guyana. Headquartered in Iere House in Piarco, the airline operates flights to the Caribbean, Nort ...
(right). * The
Gibson Hummingbird The Gibson Hummingbird is an acoustic guitar model/series produced by the Gibson Guitar Corporation. Unlike the other flat-top Gibson acoustics, the Hummingbird was Gibson's first square-shoulder dreadnought, similar to the dreadnoughts produced ...
is an acoustic guitar model/series produced by the Gibson Guitar Corporation. * During the National Costume competition of the
Miss Universe 2016 Miss Universe 2016 was the 65th Miss Universe pageant, held at the Mall of Asia Arena, in Pasay, Metro Manila, Philippines on January 30, 2017. This is the second time in the history of the competition that the pageant skipped an entire year, ...
beauty pageant, Miss Ecuador Connie Jiménez wore a costume inspired by the hummingbirds of her land that included golden wings supposed to follow the movements of her arms. However, it accidentally got damaged during the dress rehearsal, and she appeared onstage with a broken, drooping left wing.


See also

*
AeroVironment Nano Hummingbird The AeroVironment Nano Hummingbird or Nano Air Vehicle (NAV) is a tiny, remote controlled aircraft built to resemble and fly like a hummingbird, developed in the United States by AeroVironment, Inc. to specifications provided by the Defense Advan ...
– artificial hummingbird * ''
Macroglossum stellatarum The hummingbird hawk-moth (''Macroglossum stellatarum'') is a species of hawk moth found across temperate regions of Eurasia. The species is named for its similarity to hummingbirds, as they feed on the nectar of tube-shaped flowers using their ...
'' – hummingbird hawk-moth * '' Hemaris'' – sphinx moths (hummingbird moths) confused with hummingbirds


References


External links


The Hummingbird Website
Hummingbird photos, videos, articles, links, frequently asked questions
High-resolution photo gallery of almost 100 species


* ttps://web.archive.org/web/20170301202153/http://www.learner.org/jnorth/tm/humm/tongue_fluid_trap.html Video of hummingbird tongue acting as a micropump during nectar feeding {{Authority control * * Articles containing video clips Extant Rupelian first appearances National symbols of Trinidad and Tobago Natural history of the Americas Taxa named by Nicholas Aylward Vigors