The study took place in five European countries, where male and female participants (matched for height and clothing) walked directly toward birds in city parks and other green spaces.

On average, men were able to approach about one meter closer than women before the birds flew away. The researchers measured this response by recording how close a person could get before a bird took flight (termed flight initiation distance).

Published in the British Ecological Society journal People and Nature, the findings showed the same pattern in Czechia, France, Germany, Poland, and Spain. The difference also appeared across all 37 bird species examined, including easily startled magpies and pigeons that typically allow people to approach much more closely.

Why Are Birds More Afraid of Women?

The researchers believe their findings indicate that city birds can distinguish between male and female humans. However, they have yet to determine which characteristics the birds recognize or why they appear more cautious around women.

Professor Daniel Blumstein of the University of California, Los Angeles, who helped conduct the research, said the results were convincing despite the lack of an explanation.

“I fully believe our results, that urban birds react differently based on the sex of the person approaching them, but I can’t explain them right now. We used bleeding-edge comparative analysis techniques that showed our findings were consistent across cities and species, but we simply don’t have a conclusive explanation yet.”

Dr. Yanina Benedetti of the Czech University of Life Sciences Prague, another member of the research team, said the discovery challenged her expectations about how birds respond to human observers.

“As a woman in the field, I was surprised that birds reacted to us differently. This study highlights how animals in cities ‘see’ humans, which has implications for urban ecology and equality in science. Many behavioral studies assume that a human observer is neutral, but this wasn’t the case for urban birds in our study.”

What Are Birds Detecting in Humans?

Scientists have proposed several possible explanations for the difference. Birds might be responding to chemical signals such as pheromones, variations in body shape, or differences in how men and women walk. For now, however, these ideas remain speculative, and additional experiments will be needed to identify the actual cause.

Dr. Federico Morelli of the University of Turin, a co-author of the study, said the unanswered question is one of the discovery’s most fascinating aspects.

“This is maybe the most interesting part of our study,” said Dr. Federico Morelli from the University of Turin, a co-author of the study. “We have identified a phenomenon, but we really don’t know why. However, what our results do highlight is the birds’ sophisticated ability to evaluate their environment.”

The findings suggest that urban birds may be sensitive to human characteristics that people themselves rarely notice. Identifying those signals could help researchers better understand how wildlife assesses potential threats in environments shared with humans.

Dr. Benedetti said: “Urban birds clearly react to subtle cues that humans do not easily notice. Follow-up studies could focus on individual factors such as movement patterns, scent cues, or physical traits, testing them separately rather than grouping them under observer sex. This approach would help identify the specific cues birds detect.”

More Research Is Needed to Explain the Bird Behavior

Although the investigation included 2,701 observations, the researchers emphasize that their findings are still preliminary. Further studies will be necessary to establish whether the difference between birds’ responses to men and women consistently appears in other settings and populations.

For now, the discovery points to an intriguing possibility: Birds sharing our cities may be paying attention to subtle differences between people that scientists have yet to fully understand.

Understanding how viruses construct their protective protein shells, and how that construction might be interrupted, could lead to new antiviral drugs, improved vaccines, and other medical treatments. The discovery helps explain how individual proteins consistently organize themselves into the correct structures despite having thousands of possible ways to connect.

The researchers found that viral assembly resembles navigating a complicated maze, where only certain paths lead to lasting progress. At first, protein components form weak connections that can easily break apart if the arrangement is unsuccessful. This flexibility allows the molecules to keep trying different combinations until they form particular closed structures. Once multiple connections hold these structures together, they become far more stable.

These stable arrangements serve as molecular checkpoints, narrowing the enormous number of possible assembly routes into a much smaller set of successful pathways. One especially important milestone occurs when five larger protein building blocks connect to form a closed pentagonal ring. This is the first highly stable structure in the assembly process. Once it forms, each subsequent stable stage requires fewer additional building blocks, allowing the particle to grow more quickly.

Co-lead author Dr. Roi Asor (Department of Chemistry and Kavli Institute for Nanoscience Discovery, University of Oxford) explained: “A virus has to solve an extraordinary construction problem. Its components somehow have to find the right arrangement among a huge number of possibilities, without a blueprint or machinery directing the process. We can now watch what happens molecule by molecule and see the physical rules that make it possible.”

Watching Virus Particles Assemble Molecule by Molecule

Viruses store and protect their genetic material within organized protein shells known as capsids. Depending on the virus, these shells may consist of tens or even thousands of individual protein components. Remarkably, in many cases, the proteins can arrange themselves into the correct structure without any external machinery directing their assembly.

Although scientists have investigated viral self-assembly for decades, capturing the process as it unfolds has been a major challenge. Many of the intermediate structures exist only briefly and appear in very small quantities. As a result, traditional methods have generally allowed researchers to examine the starting materials and finished particles without clearly showing how one transforms into the other.

To overcome this limitation, the Oxford researchers studied an engineered virus-like particle composed of 60 protein units. They used mass photometry, a technique developed at Oxford that determines the mass of individual molecules by measuring the light they scatter. By combining this technology with a new approach for keeping individual molecules confined and continuously observable, the team could repeatedly measure the mass of a growing particle as additional proteins attached.

This approach allowed the scientists to follow the construction process as it happened, effectively tracking the addition of individual molecular building blocks over time.

Co-first author PhD student Dan Loewenthal (Department of Chemistry and Kavli Institute for Nanoscience Discovery, University of Oxford) said: “This method lets us study the assembly process directly, we just take a video!”

Co-lead author Professor Philipp Kukura (Department of Chemistry and Kavli Institute for Nanoscience Discovery, Oxford University) said: “Until now, much of our understanding of how these structures assemble has had to be reconstructed from snapshots or theoretical models. Being able to both quantify the underlying interactions and follow one particle as it grows changes that. We can see the important intermediate structures appear and deduce a detailed model of the construction process.”

The Surprising Trick That Makes Viral Assembly Work

The results help explain how a process involving an overwhelming number of possible molecular arrangements can consistently produce the correct structure. Rather than exploring every possible route, the proteins progress through a relatively small number of stable intermediate stages that guide assembly toward completion.

The findings also clarify why the earliest stage of construction, called nucleation, is particularly difficult and why growth becomes substantially faster after the first stable structure appears.

A key part of this efficiency comes from the ability of protein building blocks to make mistakes without permanently disrupting the process. Weak initial connections allow incorrect combinations to separate, giving the proteins another opportunity to find a better arrangement. When enough components eventually connect in the correct closed configuration, the resulting structure becomes stable enough to support further growth.

Dr. Asor added: “The weak interactions give the system room to make mistakes. Most encounters don’t have to be successful: the components can separate and try again. But once enough of them come together in the right closed arrangement, the structure becomes stable, and assembly can move forward. That combination of trial and error followed by locking in successful structures is what makes the process so reliable.”

New Possibilities for Antiviral Drugs and Vaccines

By identifying the molecular interactions that control viral assembly, scientists may eventually be able to develop treatments that interfere with the construction of viral protein shells. The same insights could also support efforts to engineer virus-like particles for vaccines and other therapeutic applications.

Co-author Dr. Jack Tan (MRC Weatherall Institute of Molecular Medicine and CAMS-Oxford Institute) noted: “The ability to understand these processes at the molecular level could have important applications in vaccine development and antivirals that disrupt viral assembly.”

The implications may extend far beyond viruses. Self-assembly is essential throughout biology, helping create everything from the internal skeletons of cells to specialized molecular compartments and large protein complexes.

By making it possible to observe these intricate construction processes one molecule at a time, the Oxford team’s approach offers researchers a powerful new way to investigate how complex biological structures emerge from relatively simple interactions.

Curiosity recorded the panorama using its Mastcam on August 11, during the mission’s 4,982nd Martian day, or sol. Six separate photographs were transmitted to Earth and combined to create the sweeping view. Unlike most Mastcam photographs, the images were processed without white balancing, allowing the scene to retain the distinctive colors and lighting of the Martian morning.

Curiosity Approaches Mysterious Martian Cliffs

The yardangs stretch approximately 10 miles (16 kilometers) across the northwestern portion of Mount Sharp, a 3-mile-tall (5-kilometer-tall) mountain that Curiosity has been climbing since 2014. The rover recently achieved a major milestone, gaining 0.6 miles (1 kilometer) in elevation, a greater climb than any other rover has completed on Mars.

As Curiosity continues toward these unusual formations, researchers anticipate increasingly detailed views of the cliffs. More importantly, they hope that examining the rocks firsthand will help explain how the remarkable landscape developed.

What Mars’ Ancient Rocks Reveal About Its Past

Mount Sharp contains numerous layers of sedimentary rock, each preserving evidence from a different chapter of Martian history. Investigating these layers has helped scientists reconstruct a time billions of years ago when lakes and streams existed in this region of Mars.

As the planet’s environment changed, those bodies of water eventually disappeared, leaving deposits of salty minerals behind. Once additional material stopped accumulating on the mountain, powerful winds may have gradually eroded portions of the existing rock, carving out the distinctive yardangs visible today.

Yet the unusual appearance of this particular layer has raised questions about its origins. Its color differs from the surrounding terrain, and its rock layers are tilted in an unexpected direction. Scientists suspect that processes beyond ordinary wind erosion may have contributed to its formation.

“The yardang layer looks out of place. It’s the wrong color, the layers tilt at an odd angle, and it almost appears plastered on,” said Ashwin Vasavada, Curiosity project scientist of NASA’s Jet Propulsion Laboratory in Southern California. “But that’s what makes it exciting to reach. No one is sure exactly what created this layer, but one idea is it may be ash deposited by ancient volcanic eruptions.”

NASA Plans to Investigate the Cliffs in 2027

Curiosity is now in the second year of its fifth extended mission, which began with an investigation of unusual spiderweb-like boxwork ridges. Over roughly the next year, the rover will continue traveling through rock layers containing abundant sulfates and carbonates, minerals that provide evidence of ancient drying conditions on Mars.

Mission scientists aim to reach the bottom of the yardang formations sometime in 2027. Once there, Curiosity should be able to examine the mysterious cliffs using its robotic arm, gathering unique measurements that could help determine how they formed and reveal more about the environmental changes that shaped Mars billions of years ago.