Juba Takes on the Hummingbird

Good day, it’s Juba here again and this month I have a delightful subject to share that we all seem to love. The hummingbird, which belongs to the biological family Trochilidae, is native only to the Americas and is the smallest of all birds. Small indeed, for they only measure 3-7 inches in length. Even smaller, the bee hummingbird is about 2 inches and weighs less than 0.07 ounces! Of course, they are called hummingbirds because of the sound they make when flapping their wings at a rate of 12 beats per second in the largest species, to more than 80 beats per second in the smallest.

The hummingbird experiences sexual size dimorphisms in which males are smaller than females in small species, yet larger than females in large-bodied species. This difference in size pertains to bill size and shape as well. In many clades (groupings) females have longer, more curved bills designed to carry nectar from tall flowers. These differences in body and bill size likely evolved from mating displays of the male. Amazing as it is, the boy bird must perform complex aerial maneuvers to attract the attention of a female. Because he is usually smaller, this guy can conserve energy enough to engage in such exaggerated courtship.

As specialized nectarivores, meaning they achieve energy and nutrients from a diet consisting mainly of sugar-rich nectar produced by flowering plants, they are mainly dependent on Ornithophilous flowers. These plants have colorful, often red flowers with long tubular structures that hold the nectar. Now here’s a special fact: hummingbirds can see wavelengths into the near-ultraviolet, yet hummingbird-pollinated flowers do not reflect these wavelengths as many insect-pollinated flowers do. This biological constraint may render the hummingbird-pollinated flowers relatively inconspicuous to most insects, which reduces nectar robbing.

Excluding insects, the hummingbird has the highest metabolism of all animals while in flight. Their heart rate can reach as high as 1,260 beats per minute. When flying, oxygen consumption per gram of muscle tissue in this bird is about 10 times higher than that measured in a performing human athlete. WOW! That’s some energy. This creature is rare among vertebrates in their ability to rapidly access ingested sugars, and gain 100% of their metabolic needs. In comparison, a human athlete only uses 30%. This bird can use the nectar it consumes within 30 to 45 minutes after intake.

Now for a really cheerful note: hummingbirds have a long lifespan, especially when considering their rapid metabolism. However, many do die during their first year of life, especially between hatching and fledging. But, those that do survive usually last at least a decade or more. The longest known lifespan in the wild was of a female broad-tailed hummingbird that was tagged at one year of age, then recaptured 11 years later, making her at least 12 years old.

Known thus far, male hummingbirds do not take part in nesting. The nest itself is almost always in a cup-shaped form and it rests on a branch of a tree or shrub. According to various species, the nest ranges in size from smaller than half a walnut shell to several centimeters in diameter. Spider silk and lichen is often used to construct the nest and bind it together. The silk is unique, in that it can expand to accommodate babies. Commonly, two white eggs are laid, which incubate between 14 to 23 days. The mother feeds her nestlings on small arthropods and nectar as she inserts her bill into the babies’ mouth and regurgitates the nutrients into its crop. The nestlings stay there for 18-22 days, then leave to forage on their own. However, the mom may continue to feed the babies for another 25 days.

Hummingbirds may be esthetically pleasing, but they have an extraordinary purpose beyond that. These birdies ingest so much sugar that their blood sugar levels remain high enough to kill or seriously hurt a human. The majority of the sugar goes straight to their muscles to fuel the constant buzz of their wings and rapid heartbeat. Other sugars end up in their liver where supercharged enzymes process them into fat that enables the bird’s migration. Biologists say there is no biological downside to this massive sugar binge, along with rapid weight gain and loss. Human conditions such as kidney failure, blindness, and stroke appear to be absent.

Because of these findings, hummingbirds have aided in the study of human obesity and diabetes. Research has concluded that what makes the hummingbird’s metabolism so extraordinary could help in discovery of what goes wrong in human metabolic disease and even novel ways to fight it. Understanding that the likely mechanism behind this bird’s remarkable metabolism is related to liver and muscle focuses on proteins, called enzymes. These enzymes seem to be accelerated in the hummingbird and able to break down sugars and fats with an efficiency dwarfing that of most other vertebrates.

Creating synthetic versions of the enzymes from the genetic code, researchers can determine how the bird’s enzymes are structurally and biochemically different from other animals. Studies compare those birds who have just eaten and those who are fasting. Doing so could solve the question of which proteins are used for food and which are reserved to burn through fat stores. Therefore, it is believed that even though humans have different enzymes, an understanding of metabolism in these animals might help to understand metabolism in general and perhaps shed new light on human disease.

So, there you have it. The next time you see or feed a hummingbird, think of these facts. These tiny animals are so very valuable and we who live here in the mountains are fortunate to see them on a daily basis. Take care and I’ll come up with something interesting for next month. After all, up here where we live is precious, especially with the plethora of animals available to entertain and delight us.



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