Nature Notes: Ruby-Throated Hummingbird
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By Ed Robinson
If I had to nominate the toughest of all the animals in nature on a pound for pound basis, I probably would go with the hummingbird. These tiny birds weigh only three to four grams, but they have a migration path that may exceed 3,000 miles. The most amazing part of their migration is a non-stop flight over the Gulf of Mexico, roughly 500 miles. It’s hard to imagine such a delicate creature managing the journey when it has such limited capacity to store the fat reserves needed for long flights. The name hummingbird is thought to have originated due to the humming sound created by their rapid wing beats, over 50 times per second.
While there are nearly 340 identified species of hummingbirds around the world, my bird book claims that the ruby-throated hummingbird is the only one breeding in the eastern part of North America. Its territory ranges from Alberta into the Maritime parts of Canada and as far south as Central and South America. They concentrate in areas where flowering plants are plentiful, since their primary energy food is nectar, which is high in various sugars (carbohydrates). Special hummingbird gardens and the use of feeding stations have made the ruby a common sight in backyards, and a delight to observe zipping to and fro. And zip around they do, reaching speeds of more than 30 miles per hour on the level and up to 60 mph in a dive.
Among the smallest of birds, an adult ruby has a length of less than four inches and a wing span of about four and a half inches, with females about 20 percent larger than the males and having longer bills. Their coloring is distinctive, with the male being brighter colored, as in most species. He has a metallic green back, bright red throat, dark bill with a black chin, dark wings and tail. The feathers can appear iridescent due to both pigment and refractory cells that vary the color depending upon the angle of viewing light. The extended bill is used to probe deep into flowers, or feeders, and a long forked tongue is used to draw in liquids. It’s interesting to note that hummingbirds have only about 1,500 feathers, among the fewest of any bird species. Their legs are quite short, perhaps to save weight, but it has the effect of reducing the birds to a shuffling movement, as opposed to walking and strutting as many birds practice. Wing bones are hollow, which is another weight saving technique.
The birds are known to make distinct but quiet calls including squeaks, chirps, whistles and buzzing noises from a short “tew” to a “tzip.” The best way to hear these calls is to sit quietly and still within a few feet of a feeding station – the birds will gradually come to accept your presence in the interest of getting to their food. While observing the birds in this manner, you will also see aggressive behavior among the birds since they are quite territorial and will attempt to defend preferred food sources from competitors.
Scientists consider that hummingbirds are evolved from the swift family, and you can observe similarities in their shape and feather structure. Like the swifts, hummingbirds are adept at catching insects in flight, from mosquitos to gnats, small bees and fruit flies. They are also known to eat aphids and spiders. These foods round out the nutrients that hummingbirds need for a balanced diet, and to build fat reserves up to half their body weight for migration flights that begin in late summer.
Hummingbirds have an extremely high metabolism, with a respiration rate at rest of 250 breaths per minute and a heart rate that can reach more than 1,200 beats per minute! To put that in perspective, a hummingbird consumes 10 times as much oxygen per gram of muscle as any elite human athlete. Thus the requirement for a great deal of food to maintain their normal rate of activity. They will eat up to 8 times an hour. A ruby can consume up to one half its own weight in sugar in a day and processes the sugar with rapid efficiency. When food sources are scarce, and at night, the hummingbird has adapted to go into a state of near hibernation, with their body temperature falling by half and the metabolic rate dropping by nearly 95 percent.
Another feature of the ruby that impresses me is their ability to maintain a very precise position while hovering in flight. When seen in slow motion flight, it is clear that the birds have a wonderful ability to adjust the angle and beat of their wings to compensate for wind, rain and the presence of other birds, allowing them to hold the ideal position for feeding at their desired target. Part of this ability is their amazing eye sight, which extends into the ultraviolet spectrum. This allows them to identify their preferred flowering plants at long distances, favoring red or orange colored blossoms. Their eyesight and brain function also allows the birds to process a great deal of data while flying rapidly around and through obstacles along their desired flight path. The birds can go from full speed to a full stop in an instant, hover in place, and then go back to full speed to their next target.
During the breeding season, the males will make a variety of display flights in their attempt to woo a female. They begin like the male woodcock, making high dives from up to 50 feet in the air. If a female takes a perch, indicating her interest, the male will begin rapid flights back and forth in front of her, hoping to win favor. The courtship and mating period lasts only a few days. Once the mating has occurred, the female is generally on her own to build a tiny nest and to raise her young. That nest is a tiny cup-shaped affair, about the size of a large thimble. It is often made from dandelion down or thistle, bound together using spider silk or pine sap, and attached to a branch on a suitable tree or shrub. The nest may have bits of lichen or moss on the outside, perhaps serving to camouflage it from predators. I have watched hummingbirds flying back and forth to obvious nesting sites but have yet to spot a nest, probably because the female prefers to build 10 to 40 feet off the ground. Typically the female will lay one to three tiny white eggs – the smallest bird’s eggs in nature. After two to three weeks of incubation, the nestlings are born, and their mother feeds them by inserting her bill into their open mouths and regurgitating food into their crop.
Last summer I was working in my garage when I heard and felt a subtle buzzing noise on my head so I brushed it off, thinking it was a bumble bee. It turned out to be a ruby and it landed on my garage floor. I carefully picked it up and set in on the grass outside and watched to see if it was going to be ok. Within five minutes, the bird shook its head and took flight, zipping away as if nothing unusual had occurred. Statistics show that these are durable little birds with an average life span of three to five, and tagged birds have lived up to a decade.
Respect for hummingbirds goes back to the Aztecs, who wore hummingbird talismans, believing that this would increase power, energy, potency and skill in warfare. Today, Trinidad and Tobago is known as “The land of the hummingbird” with the bird shown on their coat of arms, on a one cent coin, and in the emblem of the national airline. If you respect and enjoy seeing these lovely birds, then plant some trumpet creeper, cardinal flower, honeysuckle (but not the invasive kind), jewelweed, bee balm, red morning glory or other favored species. If you are not a gardener, buy an inexpensive feeder and mix one part granulated white table sugar with four parts water (no need for red dye). While the ruby-throated hummingbird is not considered a species in danger of disappearing, you will be helping these tiny birds to thrive in a very demanding environment.