Hummingbirds are tiny birds. Yet – powered by the nectar of flowers – some species can migrate more than 5,600 miles (9,000 km) a year. But as climate and land use are changing, so the locations of wildflowers are changing. And a new study of hummingbirds in New Mexico shows how some hummingbirds are going into short hibernation periods overnight to conserve energy for the next day’s journey. It’s not ordinary sleeping. It’s a deeper form of sleeping, which the scientists call torpor. The scientists announced their results on January 15, 2025. They said said they’ve found specific fat levels and fat reserves that some migratory hummingbirds need to go into hibernation and then resume their journeys in the morning. And they said:
Hummingbirds apparently adjust their use of torpor to wake up in the morning with a minimum fat reserve that allows for survival on a day-to-day basis in an uncertain environment.
The scientists, from the University of New Mexico, published their study in the peer-reviewed journal Proceedings of the Royal Society B on January 15, 2025.
What are hummingbirds’ migrations like?
Hummingbirds are fascinating creatures. They might be small but they’re also resilient. Not only do they make long migrations, but also these tiny birds use a lot of energy when they move. Their wings can beat at speeds of 70 to 200 times per second. So they need an almost constant source of food.
During their travels, hummingbirds feed largely on nectar, which they drink from flowers and convert into fat. However, sometimes these birds encounter changes in land use. For example, one year the land may be fallow and unplanted. Or there may be fewer plants that produce nectar. Climate change is also making the land drier; thus, there are fewer wildflowers. So the distribution of wildflowers along migratory routes is often unpredictable.
What is torpor?
In any case, the migratory routes of these animals are becoming more and more unpredictable. To protect themselves from these challenges, hummingbirds resort to a kind of nocturnal hibernation called torpor. But instead of lasting days or months as in other animals, it lasts only a few hours.
During torpor, body temperature drops and metabolic rate slows to conserve as much energy as possible. These little creatures resort to torpor at night and wake up in the morning with a minimal reserve of fat.
In his research, Shayne R. Halter, a Ph.D. candidate in the Department of Biology at the University of New Mexico, observed two species of hummingbirds during their annual migratory journeys as they headed south in the fall, crossing through New Mexico. One is the calliope hummingbird (Selasphorus calliope) and the other is the rufous hummingbird (Selasphorus rufus).
Halter, along with Blair Wolf, a professor of biology at the University of New Mexico, and co-author Carlos Martinez del Rio, professor emeritus in the Department of Zoology and Physiology at the University of Wyoming, investigated how hummingbirds make use of torpor and maintain their fat levels.
How does torpor work?
Halter found that hummingbirds enter torpor if their evening body fat falls below a specific threshold, where maintaining a high body temperature would cause their minimum morning fat reserves to fall below a critical value. In other words, hummingbirds need a minimum fat reserve in the morning to get going until they can find their next food source. Halter said:
In my research, I use a combination of body fat and overnight metabolic measurements to determine whether hummingbirds are low on energy and how they compensate with torpor. The data I collected allows me to predict if and for how long these birds will enter torpor and how much energy reserve they require in the morning to sustain them until they can find their next meal.
He also explained what the specific limits of fat are for the two species of migratory hummingbirds he studied:
In our research on rufous and calliope hummingbirds, we found that torpor occurred when fat levels fell below 500 milligrams, and we found minimum morning fat reserves to be approximately 180 milligrams. Birds will only use torpor if needed and will adjust its duration to meet the minimum morning fat reserve.
Torpor can make hummingbirds vulnerable
Halter noted that yearly migrations are challenging for hummingbirds and often result in high mortality. The increasingly hot and dry conditions in the arid Southwest are already affecting when and where nectar is available. Furthermore, changes in land use are replacing native plants with invasive and cultivated species that do not provide nectar. According to Halter:
During torpor, hummingbirds are unaware of their surroundings, making them more vulnerable to predation and other risks. For this reason, torpor should only be used when needed.
This research, by offering a model that predicts torpor frequencies, durations and fat reserves in migratory hummingbirds, will help assess ecological health, establish their energy thresholds and limits, and guide the development of conservation strategies.
Bottom line: Some species of hummingbirds undertake long migrations and face uncertain situations. To save energy, they enter a state of hibernation called torpor. Read more about it here.
Via The University of New Mexico
Read more: Hummingbirds, tiny and colorful: Lifeform of the week
Read more: Giant hummingbirds with backpacks help discover a species
The post Hummingbirds snooze when energy is low first appeared on EarthSky.
from EarthSky https://ift.tt/AnmTfQb
Hummingbirds are tiny birds. Yet – powered by the nectar of flowers – some species can migrate more than 5,600 miles (9,000 km) a year. But as climate and land use are changing, so the locations of wildflowers are changing. And a new study of hummingbirds in New Mexico shows how some hummingbirds are going into short hibernation periods overnight to conserve energy for the next day’s journey. It’s not ordinary sleeping. It’s a deeper form of sleeping, which the scientists call torpor. The scientists announced their results on January 15, 2025. They said said they’ve found specific fat levels and fat reserves that some migratory hummingbirds need to go into hibernation and then resume their journeys in the morning. And they said:
Hummingbirds apparently adjust their use of torpor to wake up in the morning with a minimum fat reserve that allows for survival on a day-to-day basis in an uncertain environment.
The scientists, from the University of New Mexico, published their study in the peer-reviewed journal Proceedings of the Royal Society B on January 15, 2025.
What are hummingbirds’ migrations like?
Hummingbirds are fascinating creatures. They might be small but they’re also resilient. Not only do they make long migrations, but also these tiny birds use a lot of energy when they move. Their wings can beat at speeds of 70 to 200 times per second. So they need an almost constant source of food.
During their travels, hummingbirds feed largely on nectar, which they drink from flowers and convert into fat. However, sometimes these birds encounter changes in land use. For example, one year the land may be fallow and unplanted. Or there may be fewer plants that produce nectar. Climate change is also making the land drier; thus, there are fewer wildflowers. So the distribution of wildflowers along migratory routes is often unpredictable.
What is torpor?
In any case, the migratory routes of these animals are becoming more and more unpredictable. To protect themselves from these challenges, hummingbirds resort to a kind of nocturnal hibernation called torpor. But instead of lasting days or months as in other animals, it lasts only a few hours.
During torpor, body temperature drops and metabolic rate slows to conserve as much energy as possible. These little creatures resort to torpor at night and wake up in the morning with a minimal reserve of fat.
In his research, Shayne R. Halter, a Ph.D. candidate in the Department of Biology at the University of New Mexico, observed two species of hummingbirds during their annual migratory journeys as they headed south in the fall, crossing through New Mexico. One is the calliope hummingbird (Selasphorus calliope) and the other is the rufous hummingbird (Selasphorus rufus).
Halter, along with Blair Wolf, a professor of biology at the University of New Mexico, and co-author Carlos Martinez del Rio, professor emeritus in the Department of Zoology and Physiology at the University of Wyoming, investigated how hummingbirds make use of torpor and maintain their fat levels.
How does torpor work?
Halter found that hummingbirds enter torpor if their evening body fat falls below a specific threshold, where maintaining a high body temperature would cause their minimum morning fat reserves to fall below a critical value. In other words, hummingbirds need a minimum fat reserve in the morning to get going until they can find their next food source. Halter said:
In my research, I use a combination of body fat and overnight metabolic measurements to determine whether hummingbirds are low on energy and how they compensate with torpor. The data I collected allows me to predict if and for how long these birds will enter torpor and how much energy reserve they require in the morning to sustain them until they can find their next meal.
He also explained what the specific limits of fat are for the two species of migratory hummingbirds he studied:
In our research on rufous and calliope hummingbirds, we found that torpor occurred when fat levels fell below 500 milligrams, and we found minimum morning fat reserves to be approximately 180 milligrams. Birds will only use torpor if needed and will adjust its duration to meet the minimum morning fat reserve.
Torpor can make hummingbirds vulnerable
Halter noted that yearly migrations are challenging for hummingbirds and often result in high mortality. The increasingly hot and dry conditions in the arid Southwest are already affecting when and where nectar is available. Furthermore, changes in land use are replacing native plants with invasive and cultivated species that do not provide nectar. According to Halter:
During torpor, hummingbirds are unaware of their surroundings, making them more vulnerable to predation and other risks. For this reason, torpor should only be used when needed.
This research, by offering a model that predicts torpor frequencies, durations and fat reserves in migratory hummingbirds, will help assess ecological health, establish their energy thresholds and limits, and guide the development of conservation strategies.
Bottom line: Some species of hummingbirds undertake long migrations and face uncertain situations. To save energy, they enter a state of hibernation called torpor. Read more about it here.
Via The University of New Mexico
Read more: Hummingbirds, tiny and colorful: Lifeform of the week
Read more: Giant hummingbirds with backpacks help discover a species
The post Hummingbirds snooze when energy is low first appeared on EarthSky.
from EarthSky https://ift.tt/AnmTfQb
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