Trochilidaehummingbirds

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Diversity

Hummingbirds belong to the order Apodiformes, meaning, "unfooted birds." There are three families in this order: Trochilidae (hummingbirds), Hemiprocnidae (tree swifts), and Apodidae (swifts). The family Trochilidae belongs to its own Suborder, Trochili. Although the number of genera and species in this group changes continually, currently there are 102 recognized genera and 328 species of hummingbirds. The hummingbird family is divided into two sub-families: Phaethornithinae (hermits) composed of 34 species and a larger group, Trochilinae (trochilines or "typical" hummingbirds), with 294 species.

Hummingbirds feed primarily on the nectar of flowers and supplement their diet with small insects. They have evolved unique characteristics such as narrow elongated beaks, extendable tongues and hovering flight, all of which allow them to exploit nectar resources.

Most hummingbird species are polygynous (males mate with more than one female) and are sexually dimorphic (sexes do not look alike); males (especially trochilines) often have bright iridescent feathers while females have more cryptic coloration. Some male hummingbirds have elaborate ornamentation such as elongated tail feathers and iridescent crests. Male hermits display together in large groups called leks while trochilines are mainly territorial; their courtship often involves dramatic aerial displays.

Known for their small size (the smallest species of hummingbird weighs 2 g), rapid wing movements and heartbeat, hummingbirds can compensate for their high energetic requirements by going into torpor during cold nights. This is especially important for those species found at high elevation where nighttime temperatures can dip below freezing.

Hummingbirds are found in a variety of habitats and while their range includes much of the New World, most hummingbird species are Neotropical. (Campbell and Lack, 1985; ; Gill, 1995; Schuchmann, 1999)

Geographic Range

Hummingbirds are found only in the New World in the Nearctic and Neotropics. Their range extends from Alaska to Labrador in the North to Tierra del Fuego in the south and from Barbados to the Juan Fernandes islands. Most species are tropical and sub-tropical and live between 10 degrees N and 25 degrees S lattitude. More than half of all species of hummingbird are found in Brazil and Ecuador. (Campbell and Lack, 1985; ; Schuchmann, 1999; Tyrrell and Tyrell, 1985)

Habitat

Hummingbirds feed and nest in a wide variety of terrestrial habitats, both temperate and tropical. The main habitat requirement for hummingbirds is a large number of nectar producing flowers. This requirement is satisfied in a number of different habitats: arid scrub, desert oasis, coastal lowland, tropical rainforest, Neararctic pine forests, and alpine tundra. Hummingbirds can be found in habitats from coastal areas at sea level to mountainous areas at an elevation of 5000 m.

Due to the prevalence of hummingbird feeders and cultivated gardens, hummingbirds can sometimes be found in urban and suburban areas with few natural food sources. There are also some agricultural crops, such as banana and coffee that can support hummingbirds. (Campbell and Lack, 1985; ; Sargent and Sargent, 2001; Schuchmann, 1999; )

Physical Description

Hummingbirds are known for their small size, long, thin bills, and amazing agility in flight. The smallest hummingbirds, reddish hermits (Phaethornis ruber) and bee hummingbirds (Mellisuga helenae) weigh less than 2 g while giant hummingbirds (Patagona gigas) weigh 19 to 21 g. Most species weigh 2.5 to 6.5 g and are 6 to 12 cm in length. Their bills are a variety of shapes; bill length and shape are often good indicators of the types of flowers each species feeds on. Hummingbirds have extendable bifurcated tongues that are used to extract nectar from flowers.

As the name of their order, Apodiformes (“unfooted birds”) suggests, hummingbirds have characteristically small feet. They are unable to walk on the ground and will fly rather than walk in order to shift on a perch.

Hummingbirds have many skeletal and flight muscle adaptations that allow for hovering and high maneuverability in flight. They are the only birds that truly hover and are capable of both forward and backward flight. The characteristic humming sound they make in flight is caused by modified outer primary feathers and is the basis for their common name. Hummingbirds can achieve a forward speed of 45 km per hour and their wingbeat ranges from 70 to 80 beats per second in smaller birds to 10 to 15 beats per second in giant hummingbirds. Their heartbeat is equally rapid ranging from 500 to 600 beats per minute while resting to over 1000 beats per minute when active.

There are two sub-families of hummingbird, hermits (Phaethornithinae) and “typical” hummingbirds or trochilines (Trochilinae). Hermits generally have brownish, grayish and reddish colors and no iridescence. Trochilines often have iridescent feathers of metallic red, orange, green and blue. Iridescence is seen most in male hummingbirds and occurs on the head, upperparts and underparts. Some males also have elegant ornamentation such as bright throat gorgets, crests and elongated tail feathers.

Hummingbirds are sexually dimorphic. Females can be bigger than males, but males are usually more colorful and can have additional adornments. Female hummingbirds have more cryptic coloration than males, most likely so that they do not attract predators to the nest when incubating and feeding chicks. The plumage of immature birds is usually similar to that of females. (Campbell and Lack, 1985; ; Gill, 1995; Howell, 2002; Johnsgard, 1997; Sargent and Sargent, 2001; Schuchmann, 1999; ; Tyrrell and Tyrell, 1985)

  • Sexual Dimorphism
  • female larger
  • sexes colored or patterned differently
  • male more colorful
  • ornamentation

Reproduction

Hummingbirds are polygynous; males interact with females only to breed and provide no parental care. Females are responsible for nest building, incubation and post-hatching parental care. Males attract mates using song, iridescent plumage and dramatic display flights. Depending on the species, males display at lekking grounds, defended territories, traditional display grounds, or singing posts. (Campbell and Lack, 1985; ; Howell, 2002; Schuchmann, 1999)

Hummingbirds breed during the season with peak nectar availability. Most hummingbirds build cup nests, but a few build domed or semi-domed nests that provide more protection than an open cup nest. Nest height ranges from a few centimeters above the ground to 10 to 30 meters. Nests are camouflaged with lichen, moss, dead leaves, bark, etc. and are held together with spider webs. They are sometimes lined with feathers, fur, hair, or plant down. Nests take 5 to 10 days to build and are often re-used year to year.

Clutch size is two and eggs are white, non-glossy and an elliptical oval shape. Because some species of hermits will lay eggs in another female’s nest, clutches of more than two can sometimes be found. There is a 48-hour interval between egg laying. The size of hummingbird eggs range from 8 by 11 mm in bee hummingbirds (Mellisuga helenae) to 12 by 20 mm in giant hummingbirds (Patagona gigas). The average weight of an egg is 0.4 to 1.4 g. Incubation usually lasts 16 to 19 days. If females begin incubating after the first egg is laid, hatching of the two eggs can occur 48 hours apart. If she waits until the second egg is laid, hatching occurs synchronously. Nestling period is 23 to 26 days; hatchlings are altricial with almost no feathers and eyes closed. Females brood young for 7 to 12 days, at which point the young are able to control their own body temperature. Fledglings continue to be fed by the female for 18 to 25 days after they have left the nest.

Female hummingbirds can have two broods per year when conditions permit and will re-nest if a brood is lost. Most nest failure is due to depredation. (Campbell and Lack, 1985; ; Johnsgard, 1997; Schuchmann, 1999)

Only female hummingbirds are involved in parental care; they must incubate eggs, brood young hatchlings, and feed the chicks as nestlings and fledglings. Hummingbird chicks are altricial and stay in the nest for 23 to 26 days. When they first hatch, young hummingbirds have few feathers and cannot thermoregulate. The female must brood the young for 7 to 12 days until they can maintain their body temperature. Females feed nestlings nectar and arthropods approximately twice every hour. Fledglings are fed by the female for 18 to 25 days and gradually learn to forage by themselves. (Campbell and Lack, 1985; ; Schuchmann, 1999)

Lifespan/Longevity

Both male and female hummingbirds usually live from 6 to 12 years and have been known to survive up to 17 years in captivity. It is difficult to estimate annual survival, but for North American species it is thought to be 30 to 45 percent. (; Sargent and Sargent, 2001; Schuchmann, 1999; ; Stokes and Stokes, 1989; Tyrrell and Tyrell, 1985)

Behavior

Hummingbirds are solitary animals. They are polygynous and males provide no parental care. Males of many species of hummingbird are territorial and the territories, which are usually centered around a food source, are aggressively defended by their owners. Territorial individuals will perch in a conspicuous spot (often the top of a tree) and watch for intruders. If an intruder is spotted the territory holder will give warning calls, perform hovering displays while flashing iridescent feathers and if necessary, chase off the intruder. Occasionally agonistic interactions will escalate and the birds will attack each other, sometimes using their beaks as weapons. When food is scarce, territory owners will use less energetically expensive behaviors to exclude intruders. Females may also set up territories surrounding nest sites. Those hummingbirds that are not territorial are mainly trap-line feeders; they will move throughout an area and feed on numerous patches of flowers.

Hermits usually form leks and congregate on traditional lekking grounds, where females visit to choose a mate. Male hummingbirds are known for their spectacular display flights that they perform in front of females during courtship and in view of intruding males during agonistic interactions. During a display flight, a male hummingbird can ascend up to a height of 30 m or more, and will dive toward the female or intruding male (often coming within centimeters of the recipient of the display), chipping at the bottom of the dive before ascending again.

Because of their high metabolic rate and the cost of their active flight, hummingbirds spend on average 70% of their time perched (often preening). They are very curious and will investigate brightly colored objects as potential food sources. They are diurnal and forage throughout the day, with peak activity at dawn and dusk.

In order to save energy during cold nights, hummingbirds will go into torpor. During torpor their body temperature decreases 20 to 30 degrees, their heartbeat can go below 50 beats per minute and their breathing becomes irregular. Most bird species are too large to use torpor to save energy since it would take too long and use too much energy to warm back up. It can take hummingbirds as long as an hour to come out of torpor, and if they are disturbed they cannot immediately resume normal activity.

Most tropical hummingbird species do not migrate but some will change elevation in response to changing temperatures or seasons. North American hummingbirds migrate and may fly distances of more than 5,000 km round trip. Males are the first to arrive at breeding and wintering grounds and are followed by females and juveniles. Because of the energetic costs of flight some hummingbirds must increase their body weight by 50% before beginning migration. (Campbell and Lack, 1985; ; Gill, 1995; Johnsgard, 1997; Schuchmann, 1999; Skutch and Singer, 1973; Tyrrell and Tyrell, 1985)

Communication and Perception

Both male and female hummingbirds have species-specific calls. Calls are usually short, high-pitched chips but some species have more drawn-out, musical songs. Singing is used both to attract mates and deter intruders. The humming noise made by wings during flight may also be a form of communication, especially in dive displays. Nestlings in domed or semi-domed nests will make begging calls but those in open cup nests will not. Fledglings make contact calls to communicate with their mothers when they are out of sight and begging calls when they are close by. Alarm calls may also be given when predators are nearby.

Hummingbirds, like most other birds do not have a well-developed sense of smell. They have color vision and unlike most vertebrates, are sensitive to ultra-violet light between 325 to 360 nanometers. Ultra-violet perception may help the birds find food since some flowers have ultra-violet color patterns. Male coloration is a cue used by females and conspecific competitors to assess dominance, quality and species identity. (Campbell and Lack, 1985; ; Howell, 2002; Johnsgard, 1997; Schuchmann, 1999)

Food Habits

Hummingbirds are nectivores and insectivores; approximately 90% of their diet comes from nectar and 10% from arthropods (flies (Diptera), wasps (Hymenoptera), spiders (Araneae), beetles (Coleoptera), and ants (Hymenoptera)). Thin, elongated hummingbird bills are well adapted to exploit nectar sources. Hummingbird pollinated flowers are usually brightly colored, scentless and have long, tubular corollas. The shape of a hummingbird’s bill determines the species of flower it can feed on. In fact, co-evolution of flower shape and bill shape is a well-studied phenomenon. Hummingbirds have also developed specialized flight structures that allow them to hover in front of flowers while feeding. Without the ability to hover, hummingbirds would not be able to obtain nectar from flowers. In addition, hummingbirds have specialized, bifurcated tongues that they can extend to reach nectar from within a flower. They use capillary action to draw the nectar along their tongue.

Because hummingbirds have a high basal metabolic rate, they can drink their body mass in nectar in less than a day. They get some amino acids from pollen and protein from insects (which they catch by hawking or hover-gleaning). When nectar resources are scarce, hummingbirds will also feed on sap from holes in trees made by sapsuckers (Sphyrapicus).

Co-existing species of hummingbirds will specialize on certain flowers or subdivide the habitat. They will either defend nectar resources on a territory or move between patches of flower-rich areas, a behavior called traplining. (Campbell and Lack, 1985; ; Howell, 2002; Schuchmann, 1999; Skutch and Singer, 1973)

Predation

Adult hummingbirds have few predators. Known predators include snakes (Serpentes), forest falcons (Micrastur, that catch hermits during lekking), and pygmy-owls (Glaucidium). Nest predators are the biggest threat to hummingbirds. These include jays (Corvidae), toucans (Ramphastidae), and some bats (Micro-chiroptera).

Female hummingbirds have more cryptic coloration than male hummingbirds. This is thought to be an adaptation that allows the females to be more camouflaged and avoid attracting predators when incubating. Females will fly to their nests in zigzags or semi-circles to avoid leading a predator directly to the nest. Hummingbirds have also been seen mobbing predators. (Campbell and Lack, 1985; Skutch and Singer, 1973)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Many species of plants rely on hummingbirds for pollination. For some species, hummingbirds are their sole pollinators. In Brazil alone, hummingbirds pollinate 58 different plant species.

Hummingbirds often pick up nectar mites (Acari) when they visit flowers. The mites climb onto the hummingbird’s bill and into the nostrils. Here they are transported from flower to flower. The mites do not harm the birds; they reproduce on the plants and eat pollen and nectar. At least forty species of mites have been described. (Campbell and Lack, 1985; Grant and Grant, 1968; Howell, 2002; Stokes and Stokes, 1989)

  • Ecosystem Impact
  • pollinates
Commensal/Parasitic Species
  • nectar mites (Acari)

Economic Importance for Humans: Positive

In the past, hummingbirds were actively hunted for feathers that were used to make jewelry and adorn clothing. They were also captured for human amusement in zoos and private collections. Hummingbirds are still sold in markets as aphrodisiacs; although there is no scientific evidence that they work.

Beyond the ecosystem services hummingbirds provide (pollination of a wide variety of plant species), perhaps their biggest economic influence can be seen in the market for hummingbird feeders and eco-tourism. (; Schuchmann, 1999; Tyrrell and Tyrell, 1985)

Economic Importance for Humans: Negative

There are no known adverse affects of hummingbirds on humans.

Conservation Status

Two species of hummingbird are known to be extinct: Brace’s emerald (Chlorostilbon bracei) and Gould’s emerald (Chlorostilbon elegans). There are 9 species listed as critically endangered by the IUCN, 11 listed as endangered and 9 listed as vulnerable. Major threats to hummingbirds are habitat loss, degradation, and fragmentation. Most of the North American species are protected under the Migratory Bird Treaty Act. No hummingbirds are listed by ESA, but almost all, if not all are listed by CITES.

Habitat destruction in the tropics does not threaten hummingbirds as much as it does some other Neotropical species. Hummingbirds can usually find nesting habitat even in human modified landscapes; cleared areas may still produce flowering plants and some plantations (banana and coffee) can support hummingbirds. Feeders and garden flowers have also allowed population and range increases in some North American species. ("UNEP-WCMC Species Database: CITES-Listed Species", 2003; ; IUCN, 2002; Sargent and Sargent, 2001; Schuchmann, 1999; ; Threatened and Endangered Species System, 2003; U.S. Fish and Wildlife Service, date unknown)

  • IUCN Red List [Link]
    Not Evaluated

Contributors

Alaine Camfield (author), Animal Diversity Web.

Kari Kirschbaum (editor), Animal Diversity Web.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

diurnal
  1. active during the day, 2. lasting for one day.
drug

a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease

ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

herbivore

An animal that eats mainly plants or parts of plants.

insectivore

An animal that eats mainly insects or spiders.

internal fertilization

fertilization takes place within the female's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

migratory

makes seasonal movements between breeding and wintering grounds

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nectarivore

an animal that mainly eats nectar from flowers

omnivore

an animal that mainly eats all kinds of things, including plants and animals

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

polygynous

having more than one female as a mate at one time

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

sexual ornamentation

one of the sexes (usually males) has special physical structures used in courting the other sex or fighting the same sex. For example: antlers, elongated tails, special spurs.

solitary

lives alone

suburban

living in residential areas on the outskirts of large cities or towns.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tundra

A terrestrial biome with low, shrubby or mat-like vegetation found at extremely high latitudes or elevations, near the limit of plant growth. Soils usually subject to permafrost. Plant diversity is typically low and the growing season is short.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

visual

uses sight to communicate

References

2003. "UNEP-WCMC Species Database: CITES-Listed Species" (On-line). Accessed November 14, 2003 at http://www.cites.org/eng/resources/species.html.

Campbell, B., E. Lack. 1985. A Dictionary of Birds. Vermillion: Buteo Books.

Gill, F. 1995. Ornithology, Second Edition. New York: W.H. Freeman and Company.

Grant, K., V. Grant. 1968. Hummingbirds & Their Flowers. New York: Columbia University Press.

Howell, S. 2002. Hummingbirds of North America, The Photographic Guide. San Diego: AP Natural World.

IUCN, 2002. "The IUCN Red List of Threatened Species" (On-line). Accessed September 19, 2003 at http://www.redlist.org/.

Johnsgard, P. 1997. The Hummingbirds of North America, Second Edition. London: Christopher Helm (Publishers) Ltd., A & C Black.

Payne, R. 2003. "Bird Families of the World" (On-line). Accessed September 19, 2003 at http://www.ummz.lsa.umich.edu/birds/Bird_Families_of_the_World.html.

Sargent, R., M. Sargent. 2001. Hummingbirds. Pp. 357-365 in C Elphick, J Dunning, D Sibley, eds. The Sibley Guide to Bird Life and Behavior. New York: Alfred A. Knopf.

Schuchmann, K. 1999. Family Trochilidae. J del Hoyo, A Elliott, S Jordi, eds. Handbook of the Birds of the World, Vol. 5. Barcelona: Lynx Edicions.

Sibley, C., J. Ahlquist. 1990. Phylogeny and Classification of Birds, A study in Molecular Evolution. New Haven: Yale University Press.

Skutch, A., A. Singer. 1973. The Life of the Hummingbird. New York: Crown Publishers, Inc.

Stokes, D., L. Stokes. 1989. The Hummingbird Book. Boston: Little, Brown and Company.

Threatened and Endangered Species System, 2003. "U.S. Listed Vertebrate Animal Species Report by Taoxonomic Group" (On-line). Accessed November 14, 2003 at http://ecos.fws.gov/tess_public/TESSWebpageVipListed?code=V&listings=0#B.

Tyrrell, E., R. Tyrell. 1985. Hummingbirds, Their Life and Behavior. New York: Crown Publishers.

U.S. Fish and Wildlife Service, date unknown. "Birds Protected by the Migratory Bird Treaty Act" (On-line). Accessed November 14, 2003 at http://migratorybirds.fws.gov/intrnltr/mbta/mbtintro.html.