Anna's hummingbird

Anna's hummingbird
Male flying
Female hovering
Conservation status
Least Concern  (IUCN 3.1)[1]
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Clade:	Strisores
Order:	Apodiformes
Family:	Trochilidae
Genus:	Calypte
Species:	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

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.

Taxonomy

Anna's hummingbird was

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]

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

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

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

Anna's hummingbird is found along the western coast of North America, from southern Canada to northern

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

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

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]

Torpor

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 than at lower elevations.^[16]

Behavior

Pollination

While collecting

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.[24] Each twist lasts four-hundredths of a second and applies 34 times the force of gravity on the bird's head.^[24]

Locomotion

During hovering flight, Anna's hummingbirds maintain high wingbeat frequencies accomplished by their large

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.[26] 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".^[27][28]

Breeding

Open-

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.^[31] It was later determined to be a hybrid between an Anna's hummingbird and a black-chinned hummingbird.^[32][33]

Urbanization

In the 2017 Vancouver Official City Bird Election, Anna's hummingbird was named the official bird of the city of

• 
  Female feeding
• 
  A female
• 
  A male
• 
  Adult male
• 
  A juvenile
• 
  California

  molt plumage
• 
  Female in California
• 
  Feeding, Vancouver Island

References

External links

Wikimedia Commons has media related to Anna's Hummingbird.

Wikispecies has information related to Calypte anna.

• Anna's hummingbird Species Account – Cornell Lab of Ornithology

• Anna's Hummingbird photo gallery at VIREO (Drexel University)