Aug 2, 2017 | Featured in: Watching Backyard Birds, August 2017

The Diversity of Hummingbirds

Rufous hummingbird, male.
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It was bright orange! I couldn't believe my eyes, but there it was: an orange hummingbird at a nectar feeder in Bloomington, Indiana. As a lifelong easterner, I had seen only one species of hummingbird: the ruby-throated. I had seen photos of North America's two orange hummingbirds (rufous and Allen's) in bird field guides, but I never expected one to turn up in my Midwestern town.

In the Pacific Northwest, where they breed, rufous hummingbirds are common in the summer. After breeding, most male rufous hummingbirds head south throughout the West, but stragglers and birds with wanderlust regularly turn up across much of the continent. Some rufous hummingbirds overwinter in the Southeast, so maybe the little guy I saw was taking the scenic route through Indiana on his southerly migration from Vancouver to Tallahassee.

The adult male rufous is the only North American hummingbird with an orange back. But not all adult male rufous hummingbirds have that distinctive characteristic. Some have a green back, making them very similar to adult male Allen's hummingbirds. The adult male of both of those species has an orange belly and a lot of orange in his tail, too. The species are best distinguished by their range. Allen's hummingbirds generally stay close to the California coast during breeding season, and are year-round residents of southern California.

The females and juveniles of both species have a green back, a pale belly, with orange under the wings. Bird watchers in southern California can host both species at their nectar feeders, and struggle to distinguish them with certainty.

Nine species of hummingbirds have substantial breeding areas in North America, and six others nest in extreme southeastern Arizona. There, it's possible to tally thirteen species of hummingbird at backyard hummingbird feeders—and the ruby-throated isn't likely to show up and make it fourteen!

The ruby-throated hummingbird breeds across the eastern U.S., and west into the prairie provinces of Canada, but it is not the only eastern hummingbird. The buff-bellied hummingbird breeds in extreme southern Texas, and commonly winters along the Gulf Coast of Texas and Louisiana. It is easily distinguishable from the rubythroat: Both male and female buff-bellies have a green head and breast that, depending upon the lighting, can look almost black; both sexes also have a buff-belly—true to its name, and a red bill with a black tip. It's noticeably larger than a rubythroat. Male and female buff-bellies look similar, although the male is slightly brighter and has a more deeply forked tail.

In the West, the black-chinned hummingbird has the largest breeding range, from southern Texas, through the desert Southwest, and into the Pacific Northwest. It is a close cousin to the rubythroat, and adult females are nearly identical. Males, though, have a purple gorget—the front of the neck where a rubythroat is brilliant red.

Residents of the Pacific Coast commonly host Anna's hummingbird year 'round. While the females of that species resemble female black-chins and rubythroats, the males have an entirely red hood and white near the eye.

Most of North America's common and widespread hummingbirds are 3.5 to 4 inches from bill tip to tail tip. Some species of hummingbird that turn up in southeastern Arizona are larger, including the magnificent hummingbird, which is a whopping 5.25 inches in length. But even that is petite compared with the giant hummingbird of western South America: It is 8.5 inches long!

North America's smallest hummingbird is the calliope, which breeds in the Pacific Northwest and the mountains of California. It is only 3.25 inches long. It's not the smallest hummingbird in the world, though. That distinction is reserved for the bee hummingbird, found only in Cuba. It has a short bill (for a hummingbird), and the total length of the bird is only 2.4 inches. Males of this species are a brilliant blue. If you lived in Cuba, you might have bee hummingbirds visiting your nectar feeder.

There are about 330 species of hummingbirds in the world, and they are found only in North and South America and the Caribbean Islands. Hummingbirds don't sing, but emit chirps, squeaks, whistles and buzzes. It may be true that hummingbirds hum because they don't know the words, but their hum is not a vocalization but a sound made by their rapid wing beats—from 50 to 90 flaps per second. They have been clocked flying at more than 30 miles per hour, but they can also hover and fly backward—a feat unique to hummingbirds. Their heart rate averages 20 beats per second. This rapid motion requires a speedy metabolism and rocket fuel, which, for hummingbirds, is nectar. A hummingbird can consume many times more than its body weight in nectar every day.

Hummingbirds have forked tongues, and until recently, it was believed that hummingbird tongues were tubular, and nectar flowed up the tongue by sucking, like a straw, or by lapping, as a dog laps from a water bowl, or by capillary action. But recent high-speed video shows that the "tubes" of a hummingbird tongue "unzip" when they are in nectar, and then close up, trapping the fluid as the tongue is pulled back.

All hummingbirds also eat small insects, and a diet of nectar and insects provides all the calories and nutrients a healthy hummingbird needs. Commercial nectar mixes that tout extra vitamins and minerals are using a marketing ploy. Don't fall for it! Four parts water to one part granulated sugar mimics natural nectar.

At night, hummingbirds go into a state of deep sleep, called torpor. Their metabolism drops by about 90 percent. Body temperature falls from 104 degrees to 64, and the heart rate drops to about 4 beats per second.

In August, the population of hummingbirds in North America is at its peak, since many species produce two clutches of two young during the summer. If all the young and all the adults survived, the hummingbird population would be three times higher than it was in the spring. But the first year of life is often deadly for hummingbirds, and experts estimate that more than 50 percent die before their first birthday. The average lifespan of hummingbirds that survive their first year is believed to be 3 to 5 years, but a few banded hummingbirds have lived more than ten years.

As August turns to September, most hummingbirds will put on weight to fuel their migration. It is true that many rubythroats fly nonstop across the Gulf of Mexico. A rufous hummingbird that has nested in southern Alaska might fly 4,000 miles to its winter home in southern Mexico, stopping to refuel as necessary.

Offering nectar into the chilly weather does not delay hummingbird departure, but rather fuels it. Hummingbird experts recommend keeping a small amount of sugar-water available for stragglers. Even into October, when there are few or no takers, keep one small nectar feeder clean and supplied (although not necessarily full) of sugar-water, just in case.



About Dawn Hewitt

Dawn Hewitt is the managing editor at Watching Backyard Birds and Bird Watcher's Digest. She has been watching birds since 1978, and wrote a weekly birding column for The Herald-Times, a daily newspaper in Bloomington, Indiana, for 11 years.

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