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Anna's hummingbird

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Anna's hummingbird
Male flying
Female hovering
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Clade: Strisores
Order: Apodiformes
Family: Trochilidae
Genus: Calypte
C. anna
Binomial name
Calypte anna
(Lesson, 1829)
Range of C. anna
  Wintering range
  Breeding and wintering range

Anna's hummingbird (Calypte anna) is a North American species of hummingbird. 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 hummingbirds bred only in northern Baja California and Southern California. The transplanting of exotic ornamental plants in residential areas throughout the Pacific coast and inland deserts provided expanded nectar and nesting sites, allowing the species to expand its breeding range. Year-round residence of Anna's hummingbirds in the Pacific Northwest is an example of ecological release dependent on acclimation to colder winter temperatures, introduced plants, and human provision of nectar feeders during winter.

These birds feed on nectar from flowers using a long extendable tongue. They also consume small insects and other arthropods caught in flight or gleaned from vegetation.


Anna's hummingbird was formally described and illustrated in 1829 by the French naturalist René Lesson in his Histoire naturelle des Oiseaux-Mouches from a specimen that had been collected in California. Lesson placed it in the genus Ornismya and coined the binomial name Ornismya anna.[2][3] Anna's hummingbird is now placed in the genus Calypte that was introduced in 1856 by the English ornithologist John Gould.[4][5] Gould did not explain the derivation of the genus name but it is probably from the Ancient Greek kaluptrē meaning "woman’s veil" or "head-dress" (from kaluptō meaning "to cover"). The specific epithet anna was chosen to honour Anne d'Essling who married the ornithologist François Victor Massena, 3rd Duke of Rivoli.[6] The species is monotypic: no subspecies are recognised.[5]


Anna's hummingbirds are 3.9 to 4.3 in (9.9 to 10.9 cm) long with a wingspan of 4.7 inches (12 cm) and a weight range of 0.1 to 0.2 oz (2.8 to 5.7 g).[7] They have an iridescent bronze-green back, a pale grey chest and belly, and green flanks. Their bills are long, straight, and slender. The adult male has an iridescent crimson-red, derived from magenta, to a reddish-pink crown and gorget, which can look dull brown or gray without direct sunlight, and a dark, slightly forked tail. Females also have iridescent red gorgets, although they are usually smaller and less brilliant than the male.[7]

A male bird displaying its iridescent head feathers

The male Anna's hummingbird is the only North American hummingbird species with a red crown.[7][8] Females and juvenile males have a dull green crown, a grey throat with or without some red iridescence, a grey chest and belly, and a dark, rounded tail with white tips on the outer feathers.[8]

The male has a striking reddish-pink crown and gorget, which are strongly iridescent and dependent on the angle of illumination and observation by female or male competitor birds.[8] The iridescence results from large stacks of melanosomes in the feather barbules, occurring as layers separated by keratin.[8] The barbules reflect incident light in the manner of partially-opened Venetian blinds, enabling the iridescence – which varies the head and gorget coloration with the changing angle of light – as a coloration advantage for courtship attraction and territory defense.[8]

Male birds with elevated levels of protein in their diet have more colorful crowns and higher iridescence in their head feathers compared with male birds with low protein intake.[9]

The male's call – scratchy and metallic – is typically used as the bird perches in trees and shrubs.[7] Anna's hummingbirds have adapted to urban environments and are commonly seen in backyards and parks, and at feeders and flowering plants. Anna's hummingbirds eat flying insects.[10]

Population and trend[edit]

According to a 2021 estimate, there are 8 million Anna's hummingbirds in the western United States and Canada,[11] with the population increasing since 1970.[12] As of 2021, the International Union for Conservation of Nature Red List of Threatened Species lists Anna's hummingbird among species of least concern.[1]

Distribution and habitat[edit]

Anna's hummingbird is found along the western coast of North America, from southern Canada to northern Baja California, and inland to southern and central Arizona, extreme southern Nevada and southeastern Utah, and western Texas.[7][13] They tend to be permanent residents within their range. However, birds have been spotted far outside their range in such places as southern Alaska, Saskatchewan, New York, Florida, Louisiana, and Newfoundland.[14][15]

In response to rising temperatures at low elevations during climate change in the 21st century, Anna's hummingbirds have expanded their range into the cooler summer environments of higher-altitude (up to 2,825 metres (9,268 ft)) mountainous terrains of California, such as the Sierra Nevada.[16]

Northern range expansion[edit]

Anna's hummingbirds have the northernmost year-round range of any hummingbird. Birds have been recorded in Alaska as early as 1971, and resident in the Pacific Northwest since the 1960s, particularly increasing as a resident population during the early 21st century.[17][18] Scientists estimate that some birds overwinter and presumably breed at northern latitudes where food and shelter are available throughout winter, tolerating moderately cold winter temperatures.[17][18]

During cold temperatures, Anna's hummingbirds gradually gain weight during the day as they convert sugar to fat.[19][20]

While their range was originally limited to the chaparral of California and Baja California, it expanded northward to Oregon, Washington, and British Columbia, and east to Arizona in the 1960s and 70s.[17] This rapid expansion is attributed to the widespread planting of non-native species, such as eucalyptus, as well as the use of urban bird feeders, in combination with the species' natural tendency for extensive postbreeding dispersal.[7]

In the Pacific Northwest, the fastest growing populations occur in regions with breeding-season cold temperatures similar to those of its native range.[17] Northward expansion of Anna's hummingbird represents an ecological release associated with introduced plants, year-round nectar availability from feeders supplied by humans, milder winter temperatures possibly associated with climate change, and acclimation of the species to a winter climate cooler than its native region.[17][18] Although quantitative data are absent, it is likely that a sizable percentage of Anna's hummingbirds in the Pacific Northwest still do migrate south for winter, as of 2017.[18]

Female Anna's hummingbird in nocturnal torpor during winter; −8 °C (18 °F), near Vancouver, British Columbia. The bird remained in torpor with an unchanged position for more than 12 hours.


Anna's hummingbirds with inadequate stores of body fat or insufficient plumage are able to survive periods of subfreezing weather by lowering their metabolic rate and entering a state of torpor.[16][21]

When studied in colder temperatures at mountainous elevations, Anna's hummingbirds used torpor more frequently and for longer periods than at lower elevations.[16]



This species consumes tree sap, nectar from flowers, insects, and sugar-water mixes from feeders.[22][23] Anna's hummingbirds capture flying insects or eat insects trapped in spider webs, sometimes even the spiders themselves.[23]


While collecting nectar, Anna's hummingbird assists in plant pollination.[12] There is evidence that Anna's hummingbirds in flight generate an electrostatic charge that adheres pollen to their beaks and feathers, facilitating transfer of pollen grains to hundreds of flowers per day while foraging for nectar.[24]

Anna's hummingbirds can shake their bodies 55 times per second to shed rain while in flight, or in dry weather, to remove pollen or dirt from feathers.[25] Each twist lasts four-hundredths of a second and applies 34 times the force of gravity on the bird's head.[25]


During hovering flight, Anna's hummingbirds maintain high wingbeat frequencies accomplished by their large pectoral muscles via recruitment of motor units.[26] The pectoral muscles that power hummingbird flight are composed exclusively of fast glycolytic fibers that respond rapidly and are fatigue-resistant.[26]

Song and courtship[edit]

Song of a male Anna's hummingbird

Unlike most northern temperate hummingbirds, the male Anna's hummingbird sings during courtship. The song is thin and squeaky, interspersed with buzzes and chirps, and is drawn to over 10 seconds in duration. During the breeding season, males can be observed performing an aerial display dive over their territories. When a female flies onto a male's territory, the male rises up about 130 ft (40 m) before diving over the female. As the male approaches the bottom of the dive, it reaches an average speed of 27 m/s (89 ft/s), which is 385 body lengths per second.[27] At the bottom of the dive, the male travels 23 m/s (51 mph), and produces an audible sound produced by the tail feathers, described by some as an "explosive squeak".[28][29]


A female incubates eggs in a camouflaged nest.
Two nestlings are fed by a female hummingbird.

Open-wooded or shrubby areas and mountain meadows along the Pacific coast from British Columbia to Arizona make up C. anna's breeding habitat. The female raises the young without the assistance of the male. The female bird builds a nest in a shrub or tree, in vines, or attached to wires or other artificial substrates. The round, 3.8-to-5.1-centimetre (1.5 to 2.0 in) diameter nest is constructed of plant fibers, downy feathers and animal hair; the exterior is camouflaged with chips of lichen, plant debris, and occasionally urban detritus such as paint chips and cigarette paper.[13] The nest materials are bound together with spider silk. They are known to nest as early as mid-December and as late as June, depending on geographic location and climatic conditions.[7][30]

Anna's hummingbirds may hybridize with other species, especially the congeneric Costa's hummingbird.[13] These natural hybrids have been mistaken for new species. A bird, allegedly collected in Bolaños, Mexico, was described and named Selasphorus floresii (Gould, 1861), or Floresi's hummingbird. Several more specimens were collected in California over a long period, and the species was considered extremely rare.[31]

The specimens were the hybrid offspring of an Anna's hummingbird and an Allen's hummingbird. A single bird collected in Santa Barbara, California, was described and named Trochilus violajugulum (Jeffries, 1888), or violet-throated hummingbird.[32] It was later determined to be a hybrid between an Anna's hummingbird and a black-chinned hummingbird.[33][34]


In the 2017 Vancouver Official City Bird Election, Anna's hummingbird was named the official bird of the city of Vancouver, British Columbia.[35] Anna's hummingbirds are non-migrating residents of Seattle where they live year-round through winter, enduring extended periods of subfreezing temperatures, snow, and high winds.[36]



  1. ^ a b "Anna's hummingbird". International Union for Conservation of Nature’s Red List of Threatened Species. 2021. Retrieved 3 May 2023.
  2. ^ Lesson, René P. (1829). Histoire naturelle des Oiseaux-Mouches (in French). Paris: Arthus Bertrand. p. xxxi; plate 74.
  3. ^ Peters, James Lee, ed. (1945). Check-List of Birds of the World. Vol. 5. Cambridge, Massachusetts: Harvard University Press. p. 136.
  4. ^ Gould, John (1856). A Monograph of the Trochilidae, or Family of Humming-Birds. Vol. 4. London: self. Plates 134, 135, 136 and text (Part 11, Plates 5, 6 and 7). The 5 volumes were issued in 25 parts between 1849 and 1861. Title pages of all volumes bear the date of 1861.
  5. ^ a b Gill, Frank; Donsker, David; Rasmussen, Pamela, eds. (August 2022). "Hummingbirds". IOC World Bird List Version 12.2. International Ornithologists' Union. Retrieved 17 September 2022.
  6. ^ Jobling, James A. (2010). The Helm Dictionary of Scientific Bird Names. London: Christopher Helm. pp. 86, 48. ISBN 978-1-4081-2501-4.
  7. ^ a b c d e f g "Anna's Hummingbird". Cornell University Laboratory of Ornithology, Ithaca, NY. 2023. Retrieved 3 May 2023.
  8. ^ a b c d e Giraldo, Marco A.; Parra, Juan L.; Stavenga, Doekele G. (8 October 2018). "Iridescent colouration of male Anna's hummingbird (Calypte anna) caused by multilayered barbules". Journal of Comparative Physiology A: Neuroethology, Sensory, Neural & Behavioral Physiology. 204 (12): 965–975. doi:10.1007/s00359-018-1295-8. ISSN 0340-7594. PMC 6244987. PMID 30298342.
  9. ^ Meadows, M. G.; Roudybush, T. E.; McGraw, K. J. (25 July 2012). "Dietary protein level affects iridescent coloration in Anna's hummingbirds, Calypte anna". The Journal of Experimental Biology. 215 (16): 2742–2750. doi:10.1242/jeb.069351. ISSN 0022-0949. PMC 3404802. PMID 22837446.
  10. ^ "Anna's hummingbird". Washington NatureMapping Foundation. 2021. Retrieved 26 September 2021.
  11. ^ Stonich, Kathryn (26 April 2021). "Hummingbirds of the United States: A Photo List of All Species". American Bird Conservancy. Retrieved 7 March 2023.
  12. ^ a b English, Simon G.; Bishop, Christine A.; Wilson, Scott; Smith, Adam C. (15 September 2021). "Current contrasting population trends among North American hummingbirds". Scientific Reports. 11 (1): 18369. Bibcode:2021NatSR..1118369E. doi:10.1038/s41598-021-97889-x. ISSN 2045-2322. PMC 8443710. PMID 34526619.
  13. ^ a b c Williamson, Sheri (2001). A Field Guide to Hummingbirds of North America. New York, NY: Houghton Mifflin Harcourt. p. 199. ISBN 0-618-02496-4.
  14. ^ "Unusual Hummingbird for Idaho: Anna's Hummingbird – Calypte anna". Archived from the original on 16 May 2008. Retrieved 12 November 2008.. See distribution map on bottom of page.
  15. ^ "Pacific hummingbird found in eastern NFLD". CBC News. 24 January 2011. Archived from the original on 21 November 2012. Retrieved 10 November 2016..
  16. ^ a b c Spence, Austin R.; LeWinter, Hannah; Tingley, Morgan W. (15 May 2022). "Anna's hummingbird (Calypte anna) physiological response to novel thermal and hypoxic conditions at high elevations". Journal of Experimental Biology. 225 (10). doi:10.1242/jeb.243294. ISSN 0022-0949. PMID 35617822.
  17. ^ a b c d e Battey, C. J. (2019). "Ecological release of the Anna's hummingbird during a northern range expansion". The American Naturalist. 194 (3): 306–315. doi:10.1086/704249. ISSN 0003-0147. PMID 31553208. S2CID 164398193.
  18. ^ a b c d Greig, Emma I.; Wood, Eric M.; Bonter, David N. (5 April 2017). "Winter range expansion of a hummingbird is associated with urbanization and supplementary feeding". Proceedings of the Royal Society B: Biological Sciences. 284 (1852): 20170256. doi:10.1098/rspb.2017.0256. ISSN 0962-8452. PMC 5394677. PMID 28381617.
  19. ^ Beuchat, C.A.; Chaplin, S.B.; Morton, M.L. (1979). "Ambient temperature and the daily energetics of two species of hummingbirds, Calypte anna and Selasphorus rufus". Physiol. Zool. 52 (3): 280–295. doi:10.1086/physzool.52.3.30155751. S2CID 87185364.
  20. ^ Powers, D. R. (1991). "Diurnal Variation in Mass, Metabolic Rate, and Respiratory Quotient in Anna's and Costa's Hummingbirds" (PDF). Physiological Zoology. 64 (3): 850–870. doi:10.1086/physzool.64.3.30158211. JSTOR 30158211. S2CID 55730100.
  21. ^ Russell, S.M. (1996). In The Birds of North America, No. 226 (A. Poole and F. Gill, eds). The Academy of Natural Sciences, Philadelphia, and The American Ornithologists' Union, Washington DC
  22. ^ Peterson, Roger Tory; Peterson, Virginia Marie (1990). Peterson's Field Guide to Western Birds. Boston: Houghton Mifflin. pp. 216–217. ISBN 0-395-51424-X.
  23. ^ a b "Calypte anna: Anna's hummingbird". Animal Diversity Web, University of Michigan, Museum of Zoology. 2020. Retrieved 27 April 2024.
  24. ^ Badger, Marc; Ortega-Jimenez, Victor Manuel; von Rabenau, Lisa; Smiley, Ashley; Dudley, Robert (30 September 2015). Gruverman, Alexei (ed.). "Electrostatic charge on flying hummingbirds and its potential role in pollination". PLOS ONE. 10 (9): e0138003. Bibcode:2015PLoSO..1038003B. doi:10.1371/journal.pone.0138003. ISSN 1932-6203. PMC 4589311. PMID 26421845.
  25. ^ a b Ortega-Jimenez, VM; Dudley, R (2012). "Aerial shaking performance of wet Anna's hummingbirds". Journal of the Royal Society Interface. 9 (70): 1093–1099. doi:10.1098/rsif.2011.0608. PMC 3306655. PMID 22072447.
  26. ^ a b Altshuler, Douglas L.; Welch, Kenneth C.; Cho, Brian H.; Welch, Danny B.; Lin, Amy F.; Dickson, William B.; Dickinson, Michael H. (15 July 2010). "Neuromuscular control of wingbeat kinematics in Anna's hummingbirds (Calypte anna)". Journal of Experimental Biology. 213 (14): 2507–2514. doi:10.1242/jeb.043497. ISSN 0022-0949. PMC 2892424. PMID 20581280.
  27. ^ Clark, C.J. (2009). "Courtship dives of Anna's hummingbird offer insights into flight performance limits". Proceedings of the Royal Society B: Biological Sciences. 276 (1670): 3047–3052. doi:10.1098/rspb.2009.0508. PMC 2817121. PMID 19515669.
  28. ^ Clark, C.J.; Feo, TJ (2008). "The Anna's Hummingbird chirps with its tail: a new mechanism of sonation in birds". Proceedings of the Royal Society B: Biological Sciences. 275 (1637): 955–62. doi:10.1098/rspb.2007.1619. PMC 2599939. PMID 18230592.
  29. ^ Yollin, Patricia (8 February 2008). "How hummingbirds chirp: It's all in the tail". San Francisco Chronicle. Retrieved 10 November 2016.
  30. ^ Sheri., Williamson (2001). A field guide to hummingbirds of North America. Boston: Houghton Mifflin. ISBN 0618024956. OCLC 46660593.
  31. ^ Palmer, T.S. (September 1928). "Notes on persons whose names appear in the nomenclature of California birds" (PDF). The Condor. 30 (5): 277. doi:10.2307/1363227. JSTOR 1363227.
  32. ^ Ridgway, Robert (1892). The Humming Birds. Washington DC: Smithsonian Institution. pp. 331, 329.
  33. ^ Taylor, Walter P. (1909). "An instance of hybridization in hummingbirds, with remarks on the weight of generic characters in the Trochilidae". The Auk. 26 (3): 291–293. doi:10.2307/4070800. JSTOR 4070800.
  34. ^ Ridgway, Robert (1909). "Hybridism and generic characters in the Trochilidae". The Auk. 26 (4): 440–442. doi:10.2307/4071292. JSTOR 4071292. Retrieved 11 November 2008.
  35. ^ "Official City Bird: Anna's Hummingbird". City of Vancouver. 2019. Retrieved 6 November 2019.
  36. ^ Gregory A Green (2 October 2018). "Anna's Hummingbird: Our winter hummingbird". BirdWatching. Retrieved 6 November 2019.

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