The Secret of the Hummingbird’s Amazing Adaptation: From Digestive System to High-Altitude Flight

“They are the only birds in the world that can fly upside down and backward,” says Holly Ernst, a conservation ecologist at the University of Wyoming. “They drink pure sugar and they don’t get diabetes.”

Ernst is one of the few researchers who researches how hummingbirds adapt to the extreme pressures of their lifestyle. In the following, we will review some things that scientists have discovered about the unique adaptation of hummingbirds.

For years, most researchers believed that hummingbirds spent only about 30 percent of their day engaged in energetic activities such as flying from flower to flower and drinking nectar, and spent most of their time resting. But physiological ecologist Anusha Shankar observed these birds closely and found that they often work much harder than previously thought.

Hummingbirds use a special trick to make the most of their energy reserves: when the bird is in danger of running out of energy, it goes into hibernation or false death at night. In this dormant state, the bird’s body temperature drops to about the same temperature as the surrounding air, sometimes only a few degrees above freezing. When the bird is asleep, it is almost comatose, unable to react quickly to stimuli around it, and breathing only intermittently.

According to Shankar’s calculations, the hibernation strategy can reduce up to 95% of the energy required for hourly metabolism on cold nights. Positioning in this position is critical after days when the bird has fed less than usual, such as days after a storm. Also, it helps the birds to store energy and increase their body fat before migration.

One class of genes that seem to remain intact during hibernation are those responsible for the bird’s internal clock. “It’s important for them to do things at the right time, even when they’re asleep,” says Shankar. For example, in order for a bird to start the day well, it starts to wake up about an hour before sunrise, much earlier than receiving visible light cues.

Dealing with sugar

Hummingbirds consume about 80% of their body weight in nectar every day in order to provide the energy needed for their very high metabolism. This amount of nectar is equivalent to a person weighing about 70 kg drinking approximately 100 half-liter cans of soda daily. Of course, nectar is often much sweeter than soda.

The human intestine cannot absorb sugar at such a speed. According to Ken Welch, a comparative physiologist at the University of Toronto Scarborough, one of the causes of stomach disease in humans comes from overconsumption of soda or candy. Hummingbirds have leaky guts to deal with the onslaught of sugar. That is, the sugar in such an intestine enters the bloodstream not only through the intestinal cells but also through them. In this way, sugar is quickly removed from the intestine before it causes discomfort. Fast sugar transport, and possibly other adaptations, allow hummingbirds to reach blood sugar levels up to six times higher than those found in humans.

Welch says it’s not yet clear how hummingbirds avoid problems like glycation, but researchers are getting clues. For example, a study shows that avian proteins have fewer glycation-prone amino acids than mammalian proteins, and other amino acids are usually deep in the protein, meaning they are less exposed to circulating sugars.

Other unknown strategies for dealing with hyperglycemia may have practical benefits for the management of diabetes in humans in the future. “There may be a gold mine in the hummingbird genome,” Welch says.

One of the challenges that hummingbirds face is the change in metabolism at the end of the day. In addition to this challenge, the nectar diet also involves issues such as high water consumption. Now, let’s take a look at the adaptations of these birds in the face of both challenges.

By the end of the overnight fast, hummingbirds almost completely deplete their body’s sugar reserves. This creates the challenge of reverse metabolism. “How does this bird wake up and fly?” asks Welch. There is nothing left but fat to burn.”

Welch found that hummingbirds are remarkably capable of switching their metabolism from burning sugar to burning fat. “This action requires a huge change in the biochemical pathways involved in the process,” he says, and the change occurs within minutes, much faster than in other organisms. He adds: “If we could also have such control over our fuel consumption, we would be very happy.”

Sugar isn’t the only challenge of a nectar-rich diet. After all, nectar is mostly water, and birds that drink such large amounts of fluid must excrete a lot of it without losing electrolytes. For this reason, the kidneys of hummingbirds are specially adapted to absorb electrolytes before re-excreting them. “These birds excrete distilled water,” says Carlos Martínez del Río, a retired physiological ecologist from the University of Wyoming.

But what is the secret of hummingbirds? They gradually adapt to the conditions. “Their work is similar to the way human climbers climb peaks like Everest, climbing and taking breaks to get used to the conditions,” Williamson says. “The journey takes months.”

As access to lighter and cheaper tracking technology improves, researchers like Williamson hope to be able to track even smaller species of hummingbirds. Tracking, along with other advances in research technology, may hold many surprises about the biology of these amazing little birds.

Why does Everest get higher every year?

How did Everest become the highest mountain in the world with a difference of more than 200 meters from the next two highest peaks? Geologists say the mountain owes part of its extra height to two ancient rivers that flowed through the Himalayas and merged years ago. The erosion from the new river washed away so much rock and soil that Everest moved up to 50 meters more.

Matt Fox, a geologist at University College London and one of the authors of a new paper that examines the mystery of Everest’s height, says that the outer crust of the Earth responds to the removal of mass by gradually rising, and this is what caused the height of Everest to rise.

Rivers cause erosion, but the effects they have on the land can be unexpected. About 89,000 years ago, a powerful river combined with another river became more erosive. This merging washed away more of the Himalayan land, and the enormous weight of the crust separated the layer of earth we live on.

The large height difference between Everest and other mountains can be partly explained by the uplift force caused by the pressure under the Earth’s crust. The underground pressure started after the erosion of a large amount of rock and river soil, which is a geological phenomenon called isostatic reaction. Revival occurs when a part of the Earth’s crust that loses mass bends and floats upward due to the intense pressure of the liquid mantle beneath it. The upward pressure is greater than the downward gravitational force after the shell loses mass.

Isostatic rebound is a gradual process, moving only a few millimeters per year, but it can significantly affect the Earth’s surface over time.

“Although mountains may seem static in terms of human life, they are actually constantly moving,” said Jinzhen Dai, a geologist at the China University of Geosciences in Beijing and the author of the paper. Although the paper can only explain part of Everest’s extra height, scientists see it as a step toward calculating how the mountain grew to its current height.

The formation of Mount Everest began about 45 million years ago when the Indian tectonic plate collided with the Eurasian plate. This collision caused a part of the earth’s crust to bend and fold on a huge scale, creating the Himalayas.

Aron River.

Although the Earth’s crust appears solid, it is not. When something massive, like an ice sheet or mountain range, weighs down the crust, it bends downward; But the lower mantle is buoyant and pushes the overhanging crust upward.

When the crust neither rises nor sinks, it is in isostatic equilibrium, and Everest must be in that state. As the Indian tectonic plate moves down, it adds new material to the Himalayas, causing the mountains to grow. At the same time, rain, snow, and glaciers wash the surface of the mountain and remove rocks and materials.

The forces of material addition from below and erosion from above must cancel each other out, meaning that Everest does not grow or shrink; But the fact that Everest keeps getting taller suggests that something is upsetting this balance. One possible reason is the erosive river, which strips the surrounding land of material that weighed down the mountain, allowing Everest to rise higher.

In the shadow of Everest is the Aron River, which, like this peak, is more distinct from the surrounding rivers. The Arun takes an unusual course, first flowing along the northern Himalayas and then twisting and turning over the ridge near Everest. This shows that the upper and lower parts of the river were not always connected and that some important event caused the connection.

By simulating the rivers of the region in computer simulations, the researchers found that about 89,000 years ago, another river network gradually eroded and made its way toward the Himalayas until it finally connected to the Arun River. When these two rivers joined together, the first river took the flow of water from Arun and made it part of its network.

The Himalayas could not cope with the erosion power of the river and the crust on top of it was pushed towards the sky by the floating mantle sea, various peaks rose and Everest gained up to 50 meters of additional height.

The tallest mountain on Earth is still growing, growing by the width of a spaghetti strand every year. A combination of factors, including crustal rebound, explains Everest’s height. But Everest’s growth spurt probably won’t last forever. The balance may tip the other way and reduce the height of Everest. Like all mountain ranges, the Himalayas will go up and down.

The findings of the study have been published in the journal Nature Geoscience.