California’s Dark-Eyed Juncos Are Quietly Evolving in Plain Sight

Dark-eyed junco in Southern California (Photo: Alex Fu)

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When we step outside and see wildlife, we often think of it as unchanging. A bird on a branch, a crab in a tide pool, a lizard skittering across a sidewalk. It feels timeless. But in truth, these animals are evolving, slowly and steadily, right in front of us. As climates become more unpredictable, habitats shift, food sources change, and nature adapts. This is especially true in our cities. Built over just the past few centuries, these sprawling human environments are reshaping the natural world and pushing wildlife to adjust in new and often surprising ways.

As California’s cities have expanded and encroached upon natural landscapes, it turns out the state’s wildlife is adapting in fascinating ways. Studying these changes is central to urban evolution, or how species adapt over time, both genetically and behaviorally, to the unique pressures of city life. From coyotes navigating traffic to birds adjusting their songs to be heard over city noise, urban evolution reveals how nature is not just surviving in cities, but evolving with them. Darwin believed natural selection was too slow to observe in real time, but today we know evolution can happen rapidly, sometimes within just a few generations.

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One cool example of urban evolution in California is the story of the dark-eyed junco (Junco hyemalis), a small songbird traditionally found in mountainous forests that is now thriving in urban environments like San Diego and Los Angeles. If you’re a birder or simply someone who enjoys watching the wildlife in your backyard, you’ve almost certainly seen them. Dark-eyed juncos are small songbirds with distinctive dark heads, often spotted hopping around on the ground rather than perching at feeders. I see them all the time, pecking at the spilled seeds beneath my feeder (or, I should say feeders, as I have several…nerd alert!). It turns out they’re classic ground foragers, evolved to search for food by scratching through leaf litter or snow, uncovering seeds, insects, and other hidden bits.

Recent research has revealed that dark-eyed juncos are evolving in direct response to urban life. Traditionally migratory, these birds once spent summers breeding in cool mountain forests and winters at lower elevations. But in the early 1980s, a group of juncos broke from that pattern and settled year-round on the campus of UC San Diego. There, researchers began documenting striking behavioral shifts. The urban juncos were bolder, less fearful of humans, and had even altered their mating and nesting habits. These changes, observed over just a few decades, offer a vivid example of how quickly species can adapt to city environments, a real-time case study in urban evolution unfolding in human-shaped habitats.

University of California San Diego (Photo: Erik Olsen)

Similarly, at the University of California, Los Angeles (UCLA), a junco population has been thriving for decades, with numbers reaching approximately 300. This long-term success has provided the Yeh Lab at UCLA with a unique opportunity to study how urban environments influence the evolution and behavior of these adaptable songbirds. Their research sheds light on how juncos have adjusted to city life, offering broader insights into wildlife resilience in human-altered habitats.

“It’s impressive how rapidly these vertebrate species can evolve. In a matter of a handful of years, we can find some pretty significant changes,” Pamela Yeh, an associate professor in ecology and evolutionary biology at UCLA, told California Curated. Yeh studied the junco population at UC San Diego when she was an undergraduate student there and wanted to expand the research to the population at UCLA. Studying the two different populations may offer insights into how species evolve in urban environments.

“We want to know, does a city make you evolve?” asks Yeh. “Do the different cities make you evolve similarly? Do the birds all become smaller? Do they all become bigger? Do they all have different-sized beaks? Or is each city unique?”

Dark-eyed junco at UCLA (Photo: Sierra Glassman)

With decades of data, the work echoes the groundbreaking research of Princeton scientists Peter and Rosemary Grant, whose studies of Galápagos finches transformed our understanding of how swiftly natural selection can operate. Now, the junco studies are taking that idea further, showing evolution unfolding not on remote islands, but in the heart of our cities.

“I think it’s now really considered a model vertebrate system for urban evolution,” says Yeh.

In their natural forest environments, juncos breed in response to the changing seasons, triggered by increasing daylight hours and rising temperatures. But in urban areas like those around UCSD and UCLA, where food is plentiful year-round, juncos have begun breeding earlier than normal and throughout the year. They build nests higher off the ground, often on artificial structures, and have increased the number of clutches per breeding season. The availability of artificial light, abundant food from human sources, and fewer natural predators in the city all play roles in these behavioral shifts.

Yeh believes it’s no accident that junco populations have surged on college campuses in recent decades. In fact, she sees it as a direct response to the unique conditions these urban environments provide.

“We think it is is partially that [urban university environments] mimic the natural environment, which is a mix of meadows and tall trees. But the other thing that we think could be important is the irrigation in grassy areas that allow the juncos, even when it’s extremely hot, there are still small insects and worms to grab and feed their offspring.”

One of the most striking adaptations among urban juncos is their behavioral shift in regards to people. Unlike their shy mountain counterparts, urban juncos are much more tolerant of human presence. This is not only a matter of convenience; it’s a survival mechanism. In the city, humans are not a threat, and urban birds need to capitalize on the resources provided by their proximity to people. Their lack of fear “allows them to keep eating even when we walk by,” says Yeh.

Studying junco evolution isn’t just a scientific curiosity. It has real conservation stakes. Things haven’t been looking good for birds. An October 2019 study published in Science by the Cornell Lab of Ornithology revealed that North America has lost nearly 3 billion birds over the past 50 years, with dark-eyed juncos alone declining by 168 million. Yet their ability to adapt to urban life suggests they may have the evolutionary tools needed to weather these dramatic changes.

Beyond behavior, there are physical differences between urban and rural populations of dark-eyed juncos. Urban juncos, for example, developed duller black plumage on their heads and showed reduced white markings in their tail feathers. Yeh and her team have also documented that the wings of urban juncos are smaller, an adaptation likely driven by the demands of maneuvering through a dense, built environment rather than long-distance flight.

Ellie Diamant, currently a Ph.D. candidate in the Department of Ecology and Evolutionary Biology at UCLA in the Yeh Lab, holding a dark-eyed junco. (Photo: Ellie Diamant)

“Juncos historically were migratory birds. The ones that live in the mountains still are. But in the urban environments, we see them year-round,” says Dr. Ellie Diamant, Visiting Assistant Professor at Bard College. “So the benefits are gone for the longer-distance flight, but there seems to be more benefit for these short wings.” Diamant completed her Ph.D. in the Department of Ecology and Evolutionary Biology at UCLA in the Yeh Lab.

The dark-eyed junco is just one example of the broader phenomenon of urban evolution, where species adjust to the challenges and opportunities posed by city life. In California, this phenomenon extends beyond birds. Coyotes, for example, have become fixtures in cities like Los Angeles, adapting to scavenge food from human waste. Coastal animals like sea lions and pelicans have also made urban waterfronts their home, thriving amid the bustle of human activity. Similarly, the Western Fence Lizard has swiftly adapted to life in an urbanized environment.

Junco hatchlings at UCLA. (Photo: Sierra Glassman)

In his book Darwin Comes to Town, Dutch evolutionary biologist Menno Schilthuizen highlights the junco as an exemplar of rapid evolution in urban settings, but it also goes much further, documenting how our manmade environments are accelerating and changing the evolution of the animals and plants around us. Of course, it’s not all good news. Not by a long shot.

Studies published in Evolutionary Applications, underscore that urbanization is a double-edged sword, offering opportunities for adaptation but also introducing serious threats. In Los Angeles, for instance, the fragmentation of habitat by highways has led to the deaths of countless animals, a problem now being tackled through the construction of wildlife bridges like the Wallis Annenberg Wildlife Crossing opening in 2026, designed to reconnect critical migration routes.

Wallis Annenberg Wildlife Crossing currently under construction (Photo: State of California)

The dark-eyed junco’s ability to adapt to city life is both encouraging and a bit sobering. It shows how some wildlife can adjust and find ways to thrive even as human development spreads. But it also reflects the growing pressure we’re putting on natural ecosystems. In other words, it’s not all good, and it’s not all bad. As scientists dig deeper into urban ecology in California and elsewhere, the junco stands out as a clear example of how life shifts and changes in response to the world we’re shaping.

For those of us who live in cities, the juncos flitting through parks, pecking in our yards, and hopping across college campuses offer a chance to see evolution happening right in front of us. Nature isn’t some distant thing beyond the city limits. It’s here, threaded into the daily patterns of urban life.

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All the Fish We Did Not See – The Discovery of the Ocean’s False Bottom off California

A paper nautilus or Argonaut, a group of pelagic octopuses that dwell in the ocean’s twilight zone. (Erik Olsen)

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In the summer of 1942, aboard the USS Jasper, a team of scientists embarked on a mission off the coast of San Diego, California, a hub for U.S. Navy operations and other military activities vital for the Pacific Theater of World War II. Their goal was to test a new technology called “long-range active sonar,” developed to detect enemy submarines—specifically Japanese submarines and German U-boats—during World War II. Long-range active sonar is a technology that sends sound waves through the ocean to map and visualize the seafloor across great distances, revealing details of underwater topography and structures that would otherwise remain hidden beneath the waves.

The expedition was led by Carl F. Eyring, an accomplished acoustic physicist known for his pioneering work in sonar technology. Eyring, along with his colleagues Ralph A. Christensen and Russell W. Raitt, played crucial roles in the mission. Their combined expertise in acoustics, naval operations, and marine science made them the perfect team to explore the deep ocean with sound.

The USS *Jasper* in 1945—just a few years after scientists discovered the first evidence of the Deep Scattering Layer during a research cruise aboard the ship. (Photo: Naval History and Heritage Command)

As they deployed sonar pulses into the depths, they encountered an unexpected anomaly: a persistent, dense layer approximately 300 yards (about 274 meters) below the surface that scattered their acoustic signals. It was almost as if the ocean floor had risen, looming closer with a strange, unyielding presence that defied all explanations.

This new reading was a complete anomaly, contradicting everything they knew about the seafloor’s topology. It was as though a solid mass had somehow materialized in the depths—a mass dense enough to obscure their sonar and make the familiar landscape unrecognizable. At the same time, their signal strength readings spiked erratically, suggesting significant interference in the water.

Carl F. Eyring (Brigham Young University)

The discovery of this peculiar layer presented an intriguing puzzle to the scientists aboard the Jasper. Yet, with a war raging, they couldn’t afford to lose focus. Instead, they concentrated on measuring its dimensions and mitigating the acoustic interference it created. Determining its true nature would have to wait for another time.

It wasn’t until almost three years later, in 1945, that oceanographer Martin Johnson deployed nets into the Pacific and uncovered the truth: the layer was actually a massive cloud of marine animals, most no larger than a human finger, migrating daily from the deep ocean to the surface and back. This dense biological layer, packed with animals capable of reflecting sonar, had created the illusion of a solid mass, effectively “masking” the true depth of the ocean floor by reflecting sonar waves off the swim bladders of the fish and other marine organisms.

Bristlemouth trawled from the ocean’s twilight zone (Erik Olsen)

This phenomenon, later termed the Deep Scattering Layer (DSL), created a “false bottom” in sonar readings, revealing an unexpectedly dense concentration of biological life in a mid-ocean zone once thought to be relatively sparse. The discovery of the DSL challenged assumptions about life distribution in the ocean, showing that vast numbers of organisms—such as fish, squid, and zooplankton—populate these depths, rising and descending with daily cycles to avoid predators and optimize feeding.

The DSL is situated within the ocean’s mesopelagic zone, commonly referred to as the twilight zone, which extends from about 200 to 1,000 meters below the surface. This region is characterized by minimal sunlight penetration and hosts a diverse array of marine life. Indeed, this huge swath of biomass is exactly what the sonar was picking up. This remarkable behavior observed in this zone is the diurnal vertical migration—the largest daily movement of biomass on Earth, the world’s largest animal migration. Each evening, billions of organisms (some scientists actually believe they number into the quadrillions) including small fish like lanternfish, hatchetfish and bristlemouths, ascend toward the surface to feed under the cover of darkness, retreating to the depths at dawn to evade predators. (Bristlemouths, by the way, are said to be the most numerous vertebrate on the planet.)

Scattering layer seen on sonar (Erik Olsen)

The discovery of the DSL provided significant insights into marine biology and oceanography. The layer’s composition—primarily swarms of marine animals with gas-filled swim bladders—explained the sonar reflections that mimicked the seafloor. This understanding highlighted the abundance and biodiversity of life in the twilight zone and underscored the importance of these organisms in oceanic ecosystems.

The discovery also led over time to an understanding of the role this layer plays in the carbon cycle, the very phenomenon that helps regulate Earth’s climate. The daily migration of marine animals in this layer is not just a remarkable biological spectacle; it is also a key mechanism for transporting carbon from the ocean’s surface to its depths. As these organisms ascend at night to feed and then return to deeper waters during the day, they excrete waste and many of them die, effectively moving carbon downwards, often sequestering it in the deep ocean floor where it can remain for centuries. This process, known as the biological carbon pump, plays a vital role in mitigating the effects of carbon dioxide in the atmosphere, thus contributing to climate stability. Without the existence of the Deep Scattering Layer and its role in the carbon cycle, the Earth’s carbon balance would be significantly different, highlighting just how interconnected marine ecosystems are with global climate regulation.

In the decades following its discovery, the DSL has remained a subject of scientific inquiry. Advancements in sonar technology and deep-sea exploration have revealed the layer’s dynamic nature and its role in global carbon cycling.

Current research into the twilight zone, particularly by scientists at the Woods Hole Oceanographic Institution (WHOI), is uncovering fascinating insights into this enigmatic region of the ocean. The twilight zone remains one of the least explored parts of the ocean, despite being home to an abundance of life and playing a crucial role in global biogeochemical cycles. Woods Hole has been at the forefront of investigating this layer, employing advanced technology like remotely operated vehicles (ROVs), autonomous underwater vehicles (AUVs), submersibles, and cutting-edge acoustic techniques to understand its complex dynamics and ecosystem.

One of the leading researchers at WHOI, Dr. Heidi Sosik, has been focusing on the role that the twilight zone plays in the carbon cycle. Sosik’s work involves the use of automated imaging technologies to analyze the behavior and diversity of the organisms inhabiting this region. By documenting their daily migrations and interactions, Sosik’s team has been able to quantify the extent to which these animals contribute to carbon transport. This research is essential for understanding how much carbon is effectively being sequestered from the atmosphere through these daily migrations.

Another prominent scientist at WHOI, Dr. Andone Lavery, is working to map the twilight zone’s acoustics in unprecedented detail. Lavery’s expertise in underwater sound technology has helped reveal not only the composition of the Deep Scattering Layer but also the behaviors of its inhabitants. Lavery’s recent findings indicate that the twilight zone’s acoustic properties are far more dynamic than previously thought, and these properties can significantly affect how marine animals detect predators and prey, as well as how researchers measure biomass in this layer.

Dr. Simon Thorrold, also from WHOI, has been studying the food web dynamics within the twilight zone. Thorrold’s research has uncovered surprising insights into predator-prey relationships among mesopelagic species. Using chemical tracers, his team has been able to track the movement of nutrients through the food web, revealing that many animals from the twilight zone are integral to surface ecosystems as well, either through vertical migration or being preyed upon by larger species such as tuna, swordfish, and marine mammals.

Scientists use a Triton submersible to explore the ocean’s twilight zone in the Bahamas. (Erik Olsen)

In addition, WHOI has been collaborating with international partners on the “Twilight Zone Exploration” (TZX) project, which aims to better understand how human activities, such as fishing and climate change, are impacting this critical part of the ocean. The mesopelagic zone is increasingly targeted by commercial fishing due to the sheer biomass it holds. Dr. Sosik and her colleagues are actively studying the potential consequences of harvesting these species, considering their importance in carbon sequestration and as a key link in marine food webs.

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Together, these efforts are gradually revealing the twilight zone’s secrets, emphasizing its importance not only in regulating climate but also in maintaining the health of marine ecosystems. As the pressures of climate change and human exploitation continue to grow, understanding this mysterious part of the ocean has never been more critical.

The USS Jasper‘s encounter with the false bottom off California’s coast stands as a pivotal moment in oceanographic history. It not only unveiled the hidden complexities of the ocean’s twilight zone but also bridged the gap between military technology and marine science, leading to a deeper appreciation of the intricate and interconnected nature of Earth’s marine environments.

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Unraveling the Geology Behind Palos Verdes’ Ongoing Landslide Crisis

A neighborhood threatened by landslides at Portuguese Bend on Palos Verdes (Erik Olsen)

For decades, geologists and engineers have been aware that the Portuguese Bend region of Palos Verdes is prone to landslides. Early maps and aerial surveys from the 1930s show continuous movement from the upper hills towards the high cliffs and bluffs that reach the Pacific Ocean.

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Over the years, with a few exceptions, the ground movement was relatively slow, averaging about a foot per year. However, after the intense rains of the past year or two, the land is now shifting much more rapidly—up to 9 to 12 inches per week—plunging neighborhoods and communities built on this unstable terrain into panic and disarray. This accelerated movement has caused irreparable damage to some homes and led California to declare a state of emergency.

Aerial survey from the 1930s showing landslide potential at Portuguese Bend in Palos Verdes (Ranch Palos Verdes city government)

People have been allowed to build homes at Portuguese Bend largely due to a combination of historical oversight, demand for coastal real estate, and limited understanding of the area’s geologic instability when development first began. In the 1950s and 1960s, when much of the residential development in the area took place, there was less awareness and fewer regulations regarding the risks of building on unstable ground. Additionally, the picturesque coastal views and desirable location made Portuguese Bend an attractive area for developers and homeowners. Despite known landslide risks, building permits were often issued because of insufficient geotechnical assessments, political and economic pressures, and a lack of stringent land-use policies at the time. Over the years, as the understanding of the area’s geologic hazards has grown, there have been more restrictions and efforts to mitigate risks, but many homes already exist on land prone to movement.

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The situation is similar to building homes in fire-prone areas – well-known to Californians, of course – within the so-called Wildland-Urban Interface (WUI), where human development meets and mixes with natural landscapes, creating a high-risk zone for natural disasters.

Small landslide at Portuguese Bend in Palos Verdes (Erik Olsen)

Portuguese Bend is one of the most active landslide zones on the peninsula. Here, the earth moves continuously, almost imperceptibly at times, but the effects are undeniable. The land isn’t just sliding; it’s flowing—like a slow-moving river of rock and dirt—down a natural depression, a sort of bowl or gulch formed by the interplay of tectonic activity and erosion. This gradual yet relentless descent toward the sea is driven by a combination of factors: the underlying geology of ancient marine sediment layers, heavy rainfall, and the constant forces of gravity pulling on the steep slopes. As a result, roads buckle, homes crack, and entire sections of land shift over time.

The geological makeup of Palos Verdes is complex and varied. The most prominent rocks on the Palos Verdes Peninsula, and the most crucial in terms of slope stability, belong to the Miocene Monterey Formation, which we wrote about in a previous article. This formation, over 2,000 feet thick in some areas, has been divided into three distinct members based on their rock types: the Altamira Shale, the Valmonte Diatomite, and the Malaga Mudstone, arranged from oldest to youngest.

Portuguese Bend at Palos Verdes

The Altamira Shale primarily consists of thin-bedded sedimentary rocks formed from layers of clay, interspersed with numerous layers of tuff, or volcanic ash that has largely transformed into weak clays over time. Thick deposits of volcanic ash, laid down millions of years ago, have been compacted into a clay-like material known as bentonite. When bentonite comes into contact with water, it becomes extremely slippery, acting like a natural lubricant. This slippery nature has been a major factor in triggering landslides throughout the Rancho Palos Verdes area, where the land’s stability is continually undermined by these underlying geological conditions.

Another factor contributing to landslides is the region’s tectonic activity. Palos Verdes sits above several active faults, including the Palos Verdes Fault. The movement along these faults exerts stress on the rock formations, leading to fractures and cracks that weaken the slopes. These cracks often become pathways for water to seep into the ground, further destabilizing the already precarious terrain.

The road along the coast at Portuguese Point has been moving for decades, a slow but relentless reminder of the dynamic nature of California’s landscape. (Erik Olsen)

Water plays a crucial role in triggering landslides in this region. Heavy rains, especially those associated with El Niño events like the atmospheric rivers of the last few years, can lead to a rapid increase in groundwater levels. When water infiltrates the ground, it increases the pressure within the soil and rock, reducing the friction that holds everything together. In Palos Verdes, where irrigation, septic systems, and urban development are common, human activities can exacerbate this natural process by altering drainage patterns and increasing water saturation in vulnerable areas. This convergence of natural and human-made factors makes the slopes more prone to sliding, particularly during or after intense rainfall.

To combat this, construction teams have installed a series of dewatering wells and pumps to actively extract groundwater from deep within the hillside. By lowering the water table and reducing the amount of water that saturates the soil, these efforts help to decrease the pressure within the slope and mitigate the risk of further ground movement. This method of dewatering is a crucial element in stabilizing the land, as it helps prevent the soil from becoming too heavy and reduces the lubricating effect that water has on the bentonite clay layers.

Closed road at Portuguese Bend in Palos Verdes (Erik Olsen)

Coastal erosion is another critical factor. The rugged cliffs of Palos Verdes are constantly being eroded by the ocean’s waves, wind, and rain. Over time, wave action undercuts the base of the cliffs, removing the support for the upper layers and leaving them hanging precariously over the ocean. As the base erodes away, the upper cliffs become more susceptible to collapse. When combined with the weakened geology and increased groundwater levels, this coastal erosion sets the stage for dramatic landslides.

Portuguese Point cliffs are part of the constant coastal erosion process at Palos Verdes aerial photo (Erik Olsen)

Recent studies are shedding new light on why landslides in Palos Verdes continue to be a concern. Geologists are now using advanced technologies, such as ground-penetrating radar and satellite imagery, to better understand the underground conditions that contribute to landslides. A study from the University of California, Los Angeles, has explored how even minor shifts in groundwater levels, exacerbated by climate change and increasingly unpredictable weather patterns, can tip the balance and trigger significant slope failures. This research emphasizes that it’s not just the obvious heavy rainfall events that pose a threat; subtle changes in water content due to human irrigation, drought, or even slight variations in precipitation can also destabilize these slopes over time.

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Moreover, new geological mapping and subsurface studies have provided a clearer picture of the fault lines and the fractured rock layers beneath Palos Verdes. These studies suggest that the interaction between multiple fault zones may be more significant than previously thought, potentially increasing the region’s susceptibility to movement. Understanding these interactions is crucial for predicting future landslides and developing mitigation strategies.

But in the end, nature will likely have the final say.

Portuguese Bend in Palos Verdes (Erik Olsen)

The picture that emerges from these studies is one of a region where natural geological processes and human activities are in a delicate balance. It’s an ongoing fight that really offers a precarious vision of the future for residents and others who use the area for recreation. The weak rock formations, intersecting fault lines, and relentless coastal erosion create an environment where the land is always moving and on the brink of collapse. Add to this the unpredictable impacts of climate change, which can bring more intense storms and alter precipitation patterns, and it becomes clear why Palos Verdes is so prone to landslides.

Efforts to mitigate the risk are ongoing. Local governments and geologists are working to develop more effective monitoring systems and better land-use planning guidelines to manage development in these sensitive areas. Understanding the complex geology and hydrology of Palos Verdes is critical to preventing future disasters and protecting the communities that call this beautiful but unstable coastline home.

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Feathers on the Flyway: Unraveling Avian Mysteries at Bear Divide with the Moore Lab

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“Personally, I really think it’s one of the best birding spots in the world,” Ryan Terrill, science director at the Klamath Bird Observatory.

Within a 45 minute drive from the urban chaos of downtown Los Angeles, lies a natural, ornithological marvel: Bear Divide, a vital corridor for the annual migration of numerous bird species. Every year — roughly between March 15 and June 15, with peak migration between April 10 and May 20 — thousands of birds funnel through the narrow pass. The divide is a small dip in the otherwise impregnable San Gabriel mountains, allowing birds in the midst of their migration to pass through safely at relatively low altitudes. This area is not just a haven for bird enthusiasts but also a critical research site, especially for the team from the Moore Lab of Zoology at Occidental College, who have been delving into the intricacies of these migratory patterns.

The Moore Lab of Zoology is renowned for its extensive bird specimen collection, one of the largest of its kind in the world for Mexican birds.

Part of the large bird collection at the Moore Lab at Occidental College in Pasadena (Erik Olsen)

Bear Divide is strategically positioned along the Pacific Flyway, a significant north-south migratory route used by birds traveling between Alaska and Patagonia. The geographical features of the San Gabriels provide an ideal resting and feeding ground for these birds, making Bear Divide a crucial stopover during their long journeys. It’s this unique combination of location and topography that makes Bear Divide an essential component of avian migration.

The discovery of Bear Divide was a lucky happenstance. A bird researcher was conducting overnight monitoring in the spring of 2016, and when morning came, he noticed legions of small songbirds whizzing past his monitoring spot. His report caught the attention of postdoc bird scientist Ryan Terrill at Moore Lab at the time, and he began an effort to monitor the birds. Terrill and his team would ultimately record as many as 20,000 birds in a single morning.

“It really is overwhelming to stand on the road and have 5,000 birds of 80 species fly by your knees in a morning,” Terrill said. The effort has continued to this day with startling results. Terrill has since left and is now the science director at the Klamath Bird Observatory.

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“Last year 2023 we counted 53,511 birds of 140 species from February to May,” said John McCormack, a professor of biology and the Director and Curator of the Moore Laboratory of Zoology. “And of course, we missed many thousands more because most travel at night. It’s easy to say that there are hundreds of thousands of birds passing through Bear Divide.”

As many as 13,000 western tanagers, lazuli buntings, chipping sparrows, hermit warblers, orioles, grosbeaks and warblers pass through Bear Divide on a single day. Why they do so, is not entirely understood. The unusual topography of Bear Divide essentially serves as a funnel for the migrating birds, with many of them shooting through the gap just a meter or two above ground.

“Personally, I really think it’s one of the best birding spots in the world,” Terrill told the LA Times.

McCormack says that the “ultimate goal is to better understand the Pacific Flyway and how it’s used, especially by small terrestrial birds. Little is known about their movements because they are hard to see and usually travel at night.”

Because many of the species sighted at Bear Divide are in steep decline. The lab says that year-to-year counts will help set a baseline for future trends that can be associated with weather, climate, and urbanization. “Tracking individual birds will give granular knowledge on how migratory birds use the landscape, which helps individuals and homeowners create corridors for them to travel,” says McCormack.

The best time to catch the show at Bear Divide is late winter early Spring. McCormack says Cliff Swallows and Lawrence’s Goldfinch are some of the early movers in March, and that by May, streaking by are Yellow Warblers, sunset-faced Western Tanagers, and bright blue Lazuli Buntings.

“There is so much we still don’t know about these birds and their world,” Lauren Hill, the site’s lead bird bander, told the Los Angeles Times. “For example, no one knows where they were before showing up here after sunrise.”

Lazuli Bunting zips past the camera at Bear Divide (Ryan Terrill)

The team is counting birds in order to establish a baseline of the populations coming through Bear Divide so they can understand how much we are changing the environment and what effect that may have on bird populations, many of which are in severe decline.

Their research spans a variety of topics, including how climate change is impacting migration routes and the effects of urbanization on bird populations. The lab has recently begun a program to put satellite trackers on birds at Bear Divide to follow individual birds, providing deep insight into their migration and resting patterns. This research is not only pivotal in understanding avian behavior but also crucial in shaping conservation policies.

One of the most fascinating aspects of Bear Divide is the sheer variety of bird species it attracts. From the diminutive hummingbirds to the impressive birds of prey, each species adds a unique dimension to the study of migration. The Moore lab’s findings have shed light on the varied responses of different species to environmental changes, offering a glimpse into the broader ecological shifts occurring across the globe.

One compelling result of the Moore Lab’s study at Bear Divide suggests that the peak of a particular species’ migration is correlated with the latitude of its breeding site. Species that breed at higher latitudes migrated through Bear Divide at later dates. It’s also unusual in the West for species to migrate during the day. Most species of birds using the Pacific Flyway are known to migrate at night.

In addition to its scientific contributions, the Moore lab is also known for its involvement in citizen science. Collaborating with local birdwatchers and volunteers, the lab extends its research capabilities and cultivates a community actively engaged in bird conservation. This collaborative approach not only enhances the breadth of their research but also underscores the importance of community involvement in conservation efforts.

Bear Divide is on public land, so anyone with a legitimate research project can get permission to work there. UCLA graduate student Kelsey Reckling, who has worked as a counter at Bear Divide since the beginning, is leading the counting efforts this Spring to understand changes in numbers of birds and species across years. Cal State L.A. graduate student Lauren Hill lea ds the group of bird banders, who catch some of the birds and record data, attaching a lightweight metal band around one leg and releasing them. Her lab mate Tania Romero is putting small, lightweight tracking devices on Yellow Warblers, which send signals to a network of tracking (MOTUS) towers across the continent.

Many bird species are under serious threat around the globe from a number of different impacts, including climate change, pesticides and habitat loss. Birds play a critical role in the health of our planet. They regulate ecosystems by preying on insects, pollinating plants, and spreading seeds. Healthy ecosystems are important for breathable air, food, and a regulated climate.

According to a 2019 study, nearly 3 billion breeding birds have been lost in North America and the European Union since 1970. That’s about 30% of the bird population in North America. The 2022 State of the Birds Report for the United States found that bird declines are continuing in almost every habitat, except wetlands. Protecting birds’ habitats, and migration routes and reducing mortality through conservation efforts are crucial to ensuring the survival of these magnificent creatures.

The research conducted at Bear Divide by the Moore lab transcends academic interests, emphasizing the interconnectivity of ecosystems and underscoring the need to preserve natural migration corridors amid urban expansion. The insights gained here are invaluable to both the scientific community and conservation efforts, highlighting the need for a balanced approach to wildlife preservation and ecological sustainability.

“What’s magical about Bear Divide is that it’s the first real place to see small, migrating birds at eye level in daylight hours,” says McCormack. “I don’t want to oversell it: it’s still a lot of small birds zinging by in a wide open place and it takes a while to get good at identifying them. But by seeing them out there, struggling against the wind and the cold, but still making progress, it gives you a real sense of how amazing their journeys are–and how we shouldn’t make them harder if there’s anything we can do about it.”

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