In a groundbreaking study, a team of scientists from the University of Massachusetts Amherst has made a remarkable discovery about bird migrations and the fuel that songbirds use during long, non-stop journeys.
Contrary to the long-held belief that these birds only consume protein towards the end of their journey, the research team found that the birds actually burn a significant amount of protein, including muscle, early in their flights. This discovery has the potential to revolutionize our understanding of avian migration and open up new research avenues.
Migratory songbirds, such as the blackpoll warbler, are known for their incredible twice-yearly flights. Their flights often cover more than 1,000 miles without stopping.
“Birds are amazing animals,” said study lead author Cory Elowe. “They are extreme endurance athletes; a bird that weighs half an ounce can fly, non-stop, flapping for 100 hours at a time, from Canada to South America. How is this possible? How do they fuel their flight?”
The energy needed for bird migration
Until now, biologists had assumed that birds primarily relied on their fat reserves to fuel these incredible feats of endurance. While fat is still a crucial part of the birds’ energy mix, this recent study has shed light on the surprising role of protein in their migratory flights.
“The birds in our tests burned fat at a consistent rate throughout their flights,” said Elowe. “But we also found that they burn protein at an extremely high rate very early in their flights, and that the rate at which they burn protein tapers off as the duration of the flight increases.”
“This is a new insight,” said study senior author Professor Alexander Gerson. “No one has been able to measure protein burn to this extent in birds before.”
“We knew that birds burned protein, but not at this rate, and not so early in their flights. What’s more, these small songbirds can burn 20% of their muscle mass and then build it all back in a matter of days.”
The research was conducted with the assistance of bird banding operators at the Long Point Bird Observatory in Ontario. During the fall, millions of birds gather near the observatory as they journey to their wintering grounds.
How the bird migration study was done
After capturing 20 blackpoll warblers and 44 yellow-rumped warblers, another migratory songbird, the researchers transported the birds to the Advanced Facility for Avian Research at Western University.
This state-of-the-art facility houses a specialized wind tunnel designed specifically for observing birds in flight. The researchers measured the birds’ fat and lean body mass before letting them fly in the wind tunnel. This was done at night to mimic their natural migration patterns.
The team would then observe the birds. At times, they would stay awake for up to 28 hours until the bird chose to rest. The researchers would then collect the bird and measure its fat and lean body mass again. They then compared the results to the pre-flight measurements.
“One of the biggest surprises was that every bird still had plenty of fat left when it chose to end its flight,” said Elowe. “But their muscles were emaciated. Protein, not fat, seems to be a limiting factor in determining how far birds can fly.”
Some bird migration questions left unanswered
The precise reasons behind the birds’ consumption of such vast stores of protein early in their journey remain unclear. However, the findings have opened up a range of possibilities for future research.
“How exactly is it possible to burn up your muscles and internal organs, and then rebuild them as quickly as these birds do,” wonders Gerson. “What insights into the evolution of metabolism might these birds yield?”
Elowe is curious about shivering – nonmigratory birds that overwinter in cold areas keep themselves warm by shivering. “This is also a feat of endurance,” said Elowe. “Do birds fuel their winter shivering spells the same way? And as the world warms, which method of coping with the cold – shivering or migrating – might be the better option for survival?”
This groundbreaking study, published in the Proceedings of the National Academy of Sciences, challenges conventional wisdom and paves the way for a deeper understanding of the fascinating world of avian migration.
What else we know about bird migration
Bird migration is a fascinating and complex phenomenon that occurs across various bird species. It involves regular, seasonal movements between breeding and wintering grounds, often covering long distances.
While our understanding of bird migration continues to grow, there are several well-established facts about this remarkable behavior:
Reasons for bird migration
Birds migrate primarily to take advantage of favorable environmental conditions and abundant food resources. Migration allows them to breed in areas with optimal conditions for raising offspring and spend the non-breeding season in locations with sufficient food supply and milder climates.
Timing and routes
Bird migration typically follows predictable seasonal patterns, with birds flying to their breeding grounds in the spring and returning to their wintering grounds in the fall. Migratory routes vary among species and can cover vast distances. Some birds, like the Arctic tern, travel over 12,000 miles during their migration, while others migrate shorter distances.
Navigation and orientation
Birds use a combination of factors to navigate during migration, including the position of the sun, stars, and the Earth’s magnetic field. They also rely on landmarks such as mountain ranges, coastlines, and rivers. Some birds are known to use their sense of smell to find their way back to their breeding or wintering sites.
Flight behavior
Migratory birds have evolved various flight behaviors to optimize their energy expenditure during migration. Soaring birds, like raptors and storks, take advantage of thermal updrafts to gain altitude without flapping their wings. Other birds, like ducks and geese, fly in a V-formation, which reduces air resistance and saves energy.
Stopovers
Birds often make stopovers during migration to rest, refuel, and sometimes even molt. These stopover sites are crucial for the survival of migrating birds, providing them with food, water, and shelter. Many birds exhibit site fidelity, returning to the same stopover sites year after year.
Impact of climate change and habitat loss
Climate change and habitat loss have significant effects on bird migration patterns. Changes in temperature and precipitation can lead to shifts in the timing of migration, breeding, and food availability. Habitat loss along migratory routes and at breeding and wintering sites can have detrimental consequences for bird populations.
Bird migration monitoring
Ornithologists and birdwatchers monitor bird migration through various methods, including bird banding, satellite tracking, radar, and citizen science programs. These efforts help collect valuable data on migratory species, which can inform conservation measures and increase our understanding of bird migration patterns.
Nocturnal migration
Many bird species, especially smaller birds like songbirds, migrate during the night. Nocturnal migration is thought to have several advantages, including reduced predation risk, cooler temperatures that minimize water loss, and better use of celestial cues for navigation.
Adaptations for migration
Birds have evolved various physiological and morphological adaptations to enable long-distance migration. These adaptations include increased fat storage for energy, efficient muscle and wing structures for sustained flight, and the ability to enter a state of torpor to conserve energy during stopovers.
Conservation efforts
Bird migration faces numerous threats, including habitat loss, climate change, and human-made structures such as wind turbines and communication towers that can cause collisions. Conservation efforts aimed at protecting migratory birds and their habitats are crucial for the long-term survival of these species. This includes the preservation of stopover sites, the implementation of bird-friendly building designs, and international collaboration to protect migratory routes.
Our understanding of bird migration continues to expand as researchers uncover new information about the factors influencing migratory behavior, the physiological adaptations that enable long-distance flight, and the impacts of human activity on these extraordinary journeys.
