Allen's Hummingbird

Selasphorus sasin

Peter LaTourrette
  • TROCHILIDAE
  • Hummingbirds
  • 530,000

This hummingbird has very restricted breeding and wintering ranges. Upon arrival in coastal California and southern Oregon, the males establish territories and attract females using a complex and extravagant aerial display consisting of a J-shaped dive preceded by shuttling and accompanied by vocalizations. The species restricted range leaves it susceptible to natural disasters, disease, and habitat destruction.

Identification
Nearly identical to Rufous Hummingbird. Male has mostly rufous underparts except for the upper breast which forms a white bib. Tail feathers reddish but tipped with black and bright copper-red throat patch (known as a "gorget"). Upperparts mostly green but with red on the top side of the tail feathers and the sides of the head. Some individuals have orange rumps that can be confused with the green-backed form of the Rufous. A metallic whine is emitted from the male's wings when in flight. Adult females and juveniles have a green iridescent back, duller red on the belly than adult males, and a white throat, with or without red or green spots or streaks. Females can have a red central throat patch like a reduced version of the gorget of adult males.

While female and juvenile Allen's and Rufous Hummingbirds are difficult to distinguish from each other, adult males can be distinguished in the field by their different aerial displays. The Allen's Hummingbird begins its display with a back-and-forth shuttling, ascends slowly, and then drops in a J-shaped dive.

Distribution and Population Trends
Allen's have one of the smallest breeding ranges of all U.S. hummingbirds. They breed in a narrow strip along the Pacific coast from southwest Oregon to southern California. Within this range, two subspecies have been identified that have different migratory patterns. Selasphorus sasin sasin breeds across this range and migrates to central Mexico in the states of Mexico, Morelos, and Puebla. S. s. sedentarius is a year-round resident of 6 of the Channel Islands off the southern coast of California and on mainland in the Los Angeles vicinity. The occurrence of breeding S. s. sedentarius on mainland is a recent (20th century) expansion of their range, probably from the nearest island of Santa Catalina. They have since spread north, south, and a short distance inland. The recent colonization of S. s. sedentarius of San Miguel Island mid-20th century may be a recolonization of habitat that was once destroyed by grazing. Additional reasons for range expansion may include increased food supply in winter from gardens, hummingbird feeders, and an increase in nonnative eucalyptus and tree tobacco. The Sur del Valle de Mexico IBA supports Allen's Hummingbirds on their wintering range and the Channel Islands IBA off the California coast supports resident Allen's.

The Breeding Bird Survey (BBS) showed a 1.4% annual decline for this species from 1966 to 2000, though it is not statistically significant. However, the BBS methodology is not ideal for detecting hummingbirds, as they do not sing, males and females occupy different habitat, they are polygynous (thus their presence does not indicate a single breeding pair), and the survey is conducted after some males have left for their wintering grounds. There are only two Christmas Bird Count circles within the range of the resident S. s. sedentarius so no population trends can be determined. It is likely that while S. s. sasin is in decline, S. s. sedentarius is increasing as evidenced by its range expansion.

Ecology
The restricted range Allen's Hummingbird subspecies (S. s. sedentarius) inhabits chaparral and riparian woodlands below 300 m in elevation. The more widely distributed subspecies (S. s. sasin) inhabits mixed evergreen, riparian woodlands, eucalyptus and cypress groves, oak woodlands, and coastal scrub areas in breeding season. Males maintain territories that overlook open coastal scrub or riparian shrubs where they perch in conspicuous places. Females choose nest sites in areas where there is more tree cover. They locate the nest in shrubs and trees with dense vegetation (such as vines and thickets) anywhere from 0.5-15 meters off the ground. Nests are composed of grasses and leaves woven together with spider webs. The outside is covered with mosses and lichens and the inside is lined with downy materials. On average two dull white eggs are laid and incubated for 12-22 days. Usually two clutches per season, more for S. s. sedentarius.

Wintering habitat in Mexico for S. s. sasin characterized by forest edges and scrub clearings with flowers. Allen's diet consists of floral nectar and small insects taken from the air or from vegetation. Adult males are the first to migrate, followed by adult females, and then juveniles. Males may leave their wintering grounds as early as late fall or early winter with birds occupying the northern limits of the breeding range arriving by late February or early March. Males leave for Mexico as early as mid-May; juveniles leave by late July.

Threats
Many species of pollinators have shown decreases across the continent. Little information is available on the overall issues that are causing these declines but potential threats include habitat loss, increased use of pesticides, replacement of native plants by invasive plants. The restricted breeding and wintering range makes the species more susceptible to natural disasters, diseases, or land use changes that could wipe out significant portions of the population, especially the residents on the Channel Islands.

Conservation
Partners in Pollination/Alainza para Polinizacion, a consortium of non-profit organizations, universities, and businesses, was formed in 1995 to increase awareness of the importance of pollinators to ecosystems, encourage research and conservation on plant/pollinator interactions, and influence policy related to plant/pollinator conservation.

The Arizona-Sonora Desert Museum's Migratory Pollinators and Their Corridors project is working to educate, develop community stewardship, and conservation for plant/pollinator systems in the U.S. and Mexico (http://www.desertmuseum.org/conservation/mp/polpart.html).

What Can You Do?
Audubon's Important Bird Area program is a vital tool for the conservation of Allen's Hummingbirds as well as other species. To learn more about the Important Bird Areas program, and how you can help, visit: http://www.audubon.org/bird/iba/.

Information on where Allen's Hummingbirds occur and in what numbers is vital to conserving the species. Help in monitoring this and other species by reporting your sightings to eBird. A project of Audubon and the Cornell Lab of Ornithology, eBird is the world's first comprehensive on-line bird monitoring program: http://www.audubon.org/bird/ebird/index.html.

Volunteers are also crucial to the success of long-term monitoring programs such as the Breeding Bird Survey. The BBS helps determine the distribution of species such as the Allen's Hummingbird and monitors population trends. To find out how you can get involved, log on to: http://www.mp2-pwrc.usgs.gov/bbs/participate/.

The Southeastern Arizona Bird Observatory has a hummingbird banding station on the San Pedro River. Their website not only provides information about hummingbirds, but the station also offers hummingbird workshops for visitors, including one on hummingbird banding and one on hummingbird identification. For more information, visit: http://www.sabo.org/hummers.htm.

References
Mitchell, D. E. 2000. Allen's Hummingbird (Selasphorus sasin). In The Birds of North America, No. 501(A. Poole and F. Gill, eds.). Philadelphia: The Academy of Natural Sciences; Washington, D.C.: The American Ornithologists' Union.

Sibley, D. A. 2000. The Sibley Guide to Birds. National Audubon Society. New York: Chanticleer Press, Inc.