Anna’s hummingbird comes from the order Apodiformes, family Trochilidae, and genus Calypte.¹ C. anna was originally named after the duchess of Rivoli by René Primevére Lesson in 1829, who described the hummingbird as having a “bright sparkle of a red cap of the richest amethyst”.²

Anna’s hummingbirds are rather stocky and medium sized in comparison to other hummingbirds. They range in mass from 4 to 4.5 g, with an average length of 100 mm.³ C. anna are sexually dimorphic. However, both males and females share many characteristics, such as a green bronzy dorsal area, a drab gray ventral area, a broad tail and a medium length bill.³

Identifying C. anna is not difficult as long as you can manage a clear view. Both the males and females have a flashy metallic red on their neck. They can turn from boring to brilliant with just a turn of the head. Interestingly, studies⁴ have found that the dietary protein levels of C. anna affects the production of the iridescent coloration. Birds with high protein levels will produce more intensely hued feathers than those with a lesser protein diet.

An adult male Anna’s hummingbird perched on a branch looking very exquisite. [Link]

Adult males have a metallic rose red colour on their whole head, which can change to violet in certain lights.⁵ They may have lighter feathers around the eye. They have broad gray-edged tail feathers that are tipped with white and their back, wing-coverts, scapulars and rump are tainted a metallic bronzy green.

The modest adult female Anna’s hummingbird. [Link]

C. anna adult females have a metallic bronze colour or a bronze-green, which is duller on their pileum.⁵ Their underparts resemble that of the males except they are only faintly glossed with metallic green and slightly paler. They may have a red metallic patch in the center of their throat area.¹ Their forehead as well as their middle pair, third pair and two outer pairs of rectrices are often a somber grayish brown.

The juvenile male and females of C. anna both resemble an adult female with subtle differences. For one, the immature males have a less rounded tail and brighter colours on the neck and crown. The juvenile females lack metallic colours on the throat and are more of a pale brown.²

C. anna are one of the most vocal hummingbirds.⁶ Their songs are learned, very elaborate and rather unusual for a nonpasserine bird.² They have a call that can be described as a very sharp stit. When they are chasing they produce a dry chatter: “zrr jika jika jika jika jika” and when they are perched they produce a scratchy dry “sturee struee struee zveeee, street street”.¹ Males will rotate their head as they sing to flash their dazzling iridescence to other nearby hummingbirds.

Check out this clip of their call [Link]:

Check out this video of a male Anna’s singing! The visuals are STUNNING! [Link]

C. anna expanded their range to now be common in British Columbia as well as southern Arizona and west Texas.¹ Prior to this C. anna were mostly found on the Pacific slope of California to San Francisco Bay.² Their breeding range extends from British Columbia, down to west of New Mexico. During breeding season males are found to live in more open dwellings, while females will live in trees, such as oaks or evergreens. The non-breeding range extends from the coast of Alaska down to northern Mexico.³ C. anna is able to expand their range so effectively due to their use of urban and surburban flower gardens and artificial nectar from hummingbird feeders.⁷

C. anna may begin nesting earlier than December.¹ Females are in charge of building the nests, incubating the eggs and rearing the brood. The nest may be on a shrub or branch of a tree, and consists of plant materials, feathers, lichen or moss to camouflage and spider webs to bind it together. The brood size is typically 2 eggs. The female feeds the young, however the brooding stops as early as 12 days after hatching.⁵ The young birds become independent after about a week or two after the nestling period (18 to 23 days). Both the males and females defend their territory, with juveniles even displaying territorial behaviour just a short time after they’ve left the nest.

A female Anna’s feeding her clutch of 2. Look at how tiny they are! [Link]

Hummingbirds need to feed frequently throughout the day to make up for their extremely high metabolism. In a study⁸ conducted at Berkeley, the energy expenditure of a male Anna hummingbird was examined. It was found that perching accounted for 56% of calories expended, nectar flights: 36%, insect-catching flights: 1.3%, and defense of territory: 4.5%. Hummingbirds have an extremely fast heart rate (1,250 beats/min while in flight) and breathing rate (250 breaths/min). It is inefficient for hummingbirds to carry any extra fat storage so they will feed often while in hovering flight for a very short amounts of time. As evident in this study, their hovering flight is very expensive, costing an average of 36% of their calories per day. To avoid running at such a high metabolism all the time, hummingbirds will go into torpor overnight (avg 9 hours).⁸

C. anna mostly feed on nectar from flowers, sugar-water from feeders, sap from trees and tiny insects for protein.⁶ They have an extended narrow bill that allows them to reach their long tongue into the center of the flower while hovering.

Hummingbirds have had to evolve their form and function of flying to suite their diet. The selective pressure of having to hover while feeding from a flower has resulted in an efficient mode of flight.⁹ For one, they have a specialized wing that allows for this, with long primaries and short secondaries. 75% lift is generated on their downstroke using the pectoralis and 25% lift is generated on upstroke using the supracoracoideus, giving the bird figure-8 wing movements that, excluding hummingbirds, is only seen in a handful of other species! Another amazing feature of hummingbird flight is their ability to switch direction of wing strokes to go from forward to backwards flight.

 

We can all agree that Anna’s Hummingbirds are incredible specimens! Luckily their population is continuing to spread and grow and they remain very common within their range.³ Check out my next blog if you’d like to hear about the extremes males will go to to impress the ladies!

Also here’s a picture I took of a female Anna’s at Buttertubs Marsh:

 

Literature cited:

1. Sibley, D. Sibley Birds West: Field Guide to Birds of Western North America. Knopf: 2016.

2. Birds of North America. Anna’s Hummingbird. https://birdsna.org/Species-Account/bna/species/annhum/introduction (accessed Oct 5, 2017).

3. Animal Diversity Web. Calypte anna. http://animaldiversity.org/accounts/Calypte_anna/ (accessed Oct 5, 2017).

4. Meadows, M. G.; Roudybush, T. E.; McGraw, K. J. (2012). Dietary Protein Level Affects Iridescent Coloration in Anna’s Hummingbirds, Calypte Anna. J. Exp. Biol. [Online] 2012, 215(16), 2742-2750 http://jeb.biologists.org/content/215/16/2742.short (accessed Oct 5, 2017).

5. Johnsgard, P. A. The Hummingbirds of North America, 2nd ed.; Smithsonian Institution: 2016.

6. Audubon. Anna’s Hummingbird. http://www.audubon.org/field-guide/bird/annas-hummingbird (accessed Oct 5, 2017).

7. West, G. C. North American Hummingbirds: An Identification Guide. UNM Press: 2015. 

8. Pearson, O. P. The Daily Energy Requirements of a Wild Anna Hummingbird. The Condor. [Online] 1954, 56 (6), 317–322 https://www.jstor.org/stable/pdf/1365017.pdf?refreqid=excelsior%3A99f750dfb5aaddfc67defdd6eeb2192e (accessed Oct 5, 2017)

9. Warrick, D.; Hedrick, T.; Fernández, M. J.; Tobalske, B.; Biewener, A. Hummingbird Flight. Current Biology. [Online] 2012, 22 (12), R472-R477 http://www.sciencedirect.com/science/article/pii/S0960982212004770 (accessed Oct 5, 2017).