San Clemente Island is Where War Games and Wildlife Coexist

Loggerhead Shrike (Photo: US Fish and Wildlife Service)

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A few months ago, I took a fishing trip out to the western side of San Clemente Island. I woke at two in the morning to the rattle of the anchor chain dropping and stepped out onto the deck, expecting darkness all around us. Instead the night was alive with a strange glow. Dozens of squid boats floated offshore, their powerful lights illuminating the water with a bluish, Avatar-like brightness. The lights draw squid toward the surface before the crews scoop them up in nets.

As I knew from earlier research, and from being a long-time California resident, squid are one of California’s top commercial fisheries, a multimillion-dollar industry built around what is known as market squid. They thrive in enormous numbers in the deep waters around the Channel Islands and up toward Santa Barbara, even though the average beachgoer rarely thinks about them. From the rail of the fishing boat I was I could see vast swarms just below the surface.

Squid boat off shore San Clemente Island (Photo: Erik Olsen)

When dawn broke, San Clemente Island emerged ahead of us, and I was struck by how stark and empty it looked. In both directions stretched the same raw, rugged coastline, with almost no sign of human presence (there were what appeared to be radio towers on the top of a peak, but no people).

It felt desolate and otherworldly. But the reality is more complicated.

The island is part of the Channel Islands, a chain that trends east to west rather than the usual north–south pattern of most California ranges. The Channel Islands are often called North America’s Galápagos because they support an extraordinary number of species found nowhere else, shaped by the deep isolation that defines island biogeography (we wrote about this earlier).

San Clemente is no exception. The island is abundant in wildlife, with its own collection of rare plants and animals. But what makes it stand apart from the other islands is the scale of the military activity just beyond the barren cliffs. The U.S. Navy conducts constant training here, including missile tests, amphibious landings, and live-fire exercises. The island is considered one of the most important training grounds for the United States military, operating around the clock even as endangered species cling to survival in the canyons and plateaus nearby.

San Clemente Island looks like a long volcanic ridge from offshore, but it has been one of the most important and least visible military landscapes in California for almost a century. It is the southernmost of the Channel Islands and has been owned entirely by the U.S. Navy since the late 1930s. Over time it became a central part of Naval Base Coronado, and today its main airfield supports helicopters, jets, drones, and special operations teams that rotate through the island throughout the year.

It all seemed really interesting. I desperately wanted to go ashore, but if I’d tried, I almost certainly would have been arrested.

Live fire training exercises with mortars on San Clemente Island Photo: (Spc. William Franco Espinosa / U.S. Army National Guard)

The island began shaping military history just before World War II. In 1939, naval engineers brought early versions of the Higgins boat to San Clemente Island to test how they handled surf, wind, and timing with naval gunfire. These flat-bottomed landing craft became essential to Allied victories in places like Normandy and Guadalcanal. The island’s rugged shoreline helped the US military refine the tactics behind the amphibious assaults that defined twentieth century warfare.

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During the Cold War, San Clemente Island evolved into one of the Navy’s busiest live fire training sites. The waters around Pyramid Cove hosted decommissioned ships used as targets. Carrier air wings practiced bombing runs across the southern plateau. Marine units rehearsed ship-to-shore landings on isolated beaches, while submarines conducted simulated missions under restricted airspace. We did a short video you can watch here.

Few places on the West Coast allowed sea, air, and land forces to operate together with real weapons, and the island’s remoteness made it ideal for rehearsing missions that couldn’t take place near populated coastlines. Yet all of this is happening just about 60 miles offshore from Los Angeles. (It took us about five hours to get back).

Civilian access has always been extremely limited, which is why the island only reaches the news when something unusual happens. One widely reported event occurred in 2023, when a private pilot illegally landed a small plane on the island’s runway and then stole a Navy truck before being detained. He tried again in 2025. This kind of thing underscores how isolated and tightly controlled the installation is. For the most part, the only people who ever set foot on the island are service members using it as a sophisticated, real world training environment.

Oh, and scientists, too.

That’s because the island’s natural history has been studied intensively. Decades ago, ranching introduced goats, sheep, and invasive plants that stripped vegetation from entire hillsides. Feral cats and rats preyed greedily on ground nesting birds, and live fire exercises fragmented habitat. By the 1970s and 1980s, San Clemente Island held one of the highest concentrations of endangered species in California, but everything was under threat.

San Clemente Island looks otherworldly and barren from a fishing boat (Photo: Erik Olsen)

Enter the U.S. Fish and Wildlife Service, which worked with the military to balance military readiness with the legal requirements of the Endangered Species Act. And it’s been, by many measures, a pretty major success.

No species became more symbolic of the struggle to protect the island than the San Clemente loggerhead shrike, a lovely, black masked songbird that lives nowhere else on Earth. By the late 1990s its wild population had fallen to as few as fourteen individuals. The Navy funded a comprehensive recovery effort that included captive breeding, predator removal, and habitat reconstruction, all with the expertise help of the San Diego Zoo Wildlife Alliance. By restoring vegetation and extensive breeding, scientists released shrikes which eventually began to hunt, build territories, and raise their young. The species is now considered one of the most successful island bird recoveries in North America.

The San Clemente Island fox, once threatened by habitat loss and predation, has rebounded significantly thanks to intensive conservation efforts that stabilized its population and restored its native ecosystem. (Photo: USFWS)

And that wasn’t the only success. Once goats and sheep were removed, native shrubs and herbs began returning to the island. Endemic plants such as the San Clemente Island lotus and San Clemente Island paintbrush, responded quickly once the pressure from grazing disappeared. In 2023, after decades of habitat recovery, the Fish and Wildlife Service announced that five island species were healthy enough to be removed from the endangered species list, a pretty cool milestone that suggested a major ecological turnaround for San Clemente and the Channel Islands as a whole.

San Clemente Island lotus (Photo: USFWS)

Today, San Clemente Island remains one of the most unusual places in California. It is a live fire training range where carrier groups, SEAL teams, and Marines rehearse some of the most complex operations in the Navy. It is also a refuge where rare birds and plants have recovered after hovering near extinction. Conservation biologists and military planners now coordinate schedules, field surveys, and habitat protections to keep both missions intact. There’s an excellent documentary on this recovery effort made by SoCal PBS.

California has become a national leader in restoring damaged ecosystems. And while the state has lost much of its original wildness over the centuries, it also offers some of the most compelling examples of species and habitats recovered from the brink. San Clemente Island is more ecologically stable today than at any point in the past century, and it continues to serve as one of the Navy’s most valuable training grounds.

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The Myth of the 100-foot Whale

Blue whale off the California coast. (Photo: Erik Olsen)

Not So Big: How We Overstate the Length of the Blue Whale, Earth’s Largest Creature

One of the most extraordinary privileges of living in California, especially near the coast, is witnessing the annual arrival of blue whales. I’ve been at sea on several occasions when these giants surfaced nearby, and to see one in person, or even through my drone RC, is astonishing and unforgettable. I once had the rare and mind-blowing opportunity to swim with and film blue whales off the southern tip of Sri Lanka for a story I wrote and produced, an experience that will forever be seared into memory.

For decades, the blue whale has been celebrated as the largest creature ever to exist (Bigger than dinosaurs! True.), with many popular accounts claiming that these animals can reach lengths of 100 feet or more. Yet in all the videos, photographs, and encounters I’ve seen, not a single whale has come close to that. Still, article after article and documentary after documentary continues to repeat the claim that blue whales “reach 100 feet or more.” Nearly every whale-watching company in California repeats the claim, echoed endlessly across Instagram and TikTok.

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But is it true? Most blue whales I’ve seen off the coast of California are half that size or maybe 2/3. It felt misleading to say so otherwise. And so I did a lot of digging: reading, reaching out to experts, poring over historical records, and the fact is that no single blue whale has ever been scientifically measured at 100 feet. Close, as you will soon read, but not 100 feet or more. Especially not off the coast of California.

This discrepancy not only distorts our understanding of these magnificent creatures, but also highlights the broader issue of how media can shape and sometimes mislead public perception of scientific facts.

Blue whale tail fluke in Sri Lanka. (Photo: Erik Olsen)

In other words: the perception that blue whales commonly reach lengths of 100 feet or more likely stems from a combination of historical anecdotes, estimation errors, and a tendency to highlight extreme examples.

All that said, the blue whale (Balaenoptera musculus) is a truly magnificent creature. Hunted nearly to extinction in the 17th to 19th centuries, the blue whale has staged a hopeful recovery in the last five decades, since commercial whaling was outlawed by the international community in 1966 (although some Soviet whale hunting continued into the early 1970s). And California, in particular, has been blessed with the annual appearance of the largest population of blue whales in the world, called the Eastern North Pacific population, consisting of some 2,000 animals. That population makes an annual migration from the warm waters of Baja California to Alaska and back every year. This is the group I’ve seen off Newport Beach.

These numbers are painfully, tragically small compared to what existed before commercial whaling began. Prior to that, it was estimated that there were some 400,000 blue whales on earth. 360,000 were killed in the Antarctic alone. (IMO: this stands as one of the most shameful acts in human history).

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The International Union for Conservation of Nature estimates that there are probably between 5,000 to 15,000 blue whales worldwide today, divided among some five separate populations or groups, including the Eastern North Pacific population. Many now swim so close to shore that an entire whale-watching industry has flourished along the California coast, especially in the south, with many former fishing boats converted into whale-watching vessels..

But back to size, or, more specifically, length: there are two credible references in scientific papers of blue whales that are near 100 feet. The first is a measurement dating back to 1937. This was at an Antarctic whaling station where the animal was said to measure 98 feet. But even that figure is shrouded in some suspicion. First of all, 1937 was a long time ago, and while the size of a foot or meter has not changed, a lot of record-keeping during that time is suspect, as whales were not measured using standard zoological measurement techniques (see below). The 98-foot specimen was recorded by Lieut. Quentin R. Walsh of the US Coast Guard, who was acting as a whaling inspector of the factory ship Ulysses. Sadly, there is scant detail available about this measurement and it remains suspect in the scientific community.

Blue whale in Sri Lanka. (Photo: Erik Olsen)

The second is from a book and a 1973 paper by the late biologist Dale W. Rice, who references a single female in Antarctica whose “authenticated” measurement was also 98 feet. The measurement was conducted by the late Japanese biologist Masaharu Nishiwaki. Nishiwaki and Rice were friends, and while both are deceased, a record of their correspondence exists in a collection of Rice’s papers held by Sally Mizroch, co-trustee of the Dale W. Rice Research Library in Seattle. Reached by email, Dr. Mizroch said that Nishiwaki, who died in 1984, was a very well-respected scientist and that the figure he cited should be treated as reliable.

According to Mizroch, who has reviewed many of the Antarctic whaling records from the whaling era, whales were often measured in pieces after they were cut up, which greatly introduces the possibility for error. That is likely not the case with the 98-foot measurement, which took place in 1947 at a whaling station in Antarctica where Nishiwaki was stationed as a scientific observer.

Proper scientific measurements, the so-called “standard method”, are taken by using a straight line from the tip of the snout to the notch in the tail flukes. This technique was likely not used until well into the 20th century, said Mizroch. In fact, it wasn’t until the 1940s that the use of a metal tape measure became commonplace. According to Dan Bortolotti, author of Wild Blue: A Natural History of the World’s Largest Animal, many of the larger whales in the whaling records — especially those said to be over 100 feet — were probably measured incorrectly or even deliberately exaggerated because bonus money was paid to whalers based on the size of the animal caught.

So, according to the best records we have, the largest blue whale ever properly measured was 98 feet long. Granted, 98 feet is close to 100 feet, but it’s not 100 feet, and it’s certainly not over 100 feet, as so many otherwise reputable references state.

So, setting aside the fact that so many sources say the blue whale has reached 100 feet or more, and that there is no scientific evidence proving this, a key question to ask is how large can whales become?

Blue whale from the National Oceanic and Atmospheric Administration

Most baleen whales are so-called lunge feeders. They open their mouths wide and lunge at prey like krill or copepods, drawing in hundreds of pounds of food at a time. Lunge-feeding baleen whales, it turns out, are wonderfully efficient feeders. The larger they become, the larger their gulps are, and the more food they draw in. But they also migrate vast distances, and oftentimes have to dive deep to find prey, both of which consume a large amount of energy.

A 2019 scientific paper in Science described how a team of researchers used an ocean-going Fitbit-like tag to track whales’ foraging patterns, hoping to measure the animals’ energetic efficiency, or the total amount of energy gained from foraging, relative to the energy expended in finding and consuming prey. The team concluded that there are likely ecological limits to how large a whale can become and that maximum size in filter feeders “is likely constrained by prey availability across space and time.” That is especially the case in today’s era, when overfishing and illegal fishing, including krill harvesting in Antarctica, have reduced the amount of prey available even in regions that used to be very prolific.

Whale fall off the California Coast (Ocean Exploration Trust)

John Calambokidis, a Senior Research Biologist and co-founder of Cascadia Research, a non-profit research organization formed in 1979 based in Olympia, Washington, has studied blue whales up and down the West Coast for decades. He told California Curated that the persistent use of the 100-foot figure can be misleading, especially when the number is used as a reference to blue whales off the coast of California.

The sizes among different blue whale groups differ significantly depending on their location around the globe. Antarctic whales tend to be much bigger, largely due to the amount of available food in cold Southern waters. The blue whales we see off the coast of California, Oregon, Washington and Alaska, are part of a different group from those in Antarctica. They differ both morphologically and genetically, and they consume different types and quantities of food. North Pacific blue whales, our whales, tend to be smaller and likely have always been so. Calambokidis believes that the chances any blue whales off the West Coast of the US ever reaching anything close to 100 feet is “almost non-existent”.

I emailed Regina Asmutis-Silvia, Executive Director North America of Whale and Dolphin Conservation, to ask about this discrepancy among so many seemingly authoritative outlets. She wrote: “While it appears biologically possible for blue whales to reach or exceed lengths of 100’, the current (and limited) photogrammetry data suggest that the larger blue whales which have been more recently sampled are under 80 feet.” Photogrammetry is the process of using several photos of an object — like a blue whale — to extract a three-dimensional measurement from two-dimensional data. It is widely used in biology, as well as engineering, architecture, and many other disciplines. Photogrammetry measurements are now often acquired by drones and have proven to be a more accurate means of measuring whale size at sea.

Here’s a key point: In the early part of the 20th century and before, whales were measured by whalers for the purpose of whaling, not measured by scientists for the purpose of science. Again, none of this is to say that blue whales aren’t gargantuan animals. They are massive and magnificent, but if we are striving for precision, it is not accurate to declare, as so many articles and other media do, that blue whales reach lengths of 100 feet or more. Or to insinuate that this size is in any way common. This is not to say it’s impossible that whales grew to or above 100 feet, it’s that, according to the scientific records, none ever has.

A relevant point from Dr. Asmutis-Silvia about the early days of Antarctic whaling: “Given that whales are long-lived and we don’t know at what age each species reaches its maximum length, it is possible that we took some very big, very old whales before we started to measure what we were taking.”

In an email exchange with Jeremy Goldbogen, the scientist at Stanford who authored the study in Science above, he says that measurements with drones off California “have been as high as 26 meters” or 85 feet.

So, why does nearly every citation online and elsewhere regularly cite the 100-foot number? It probably has to do with our love of superlatives and round numbers. We have a deep visceral NEED to be able to say that such and such animal is the biggest or the heaviest or the smallest or whatever. And, when it comes down to it, 100 feet is a nice round number that rolls easily off the tongue or typing fingers.

All said, blue whales remain incredible and incredibly large animals, and deserve our appreciation and protection. Their impressive rebound over the last half-century is to be widely celebrated, but let’s not, in the spirit of scientific inquiry, overstate their magnificence. They are magnificent enough.

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Manzanitas are California’s Sculptured Survivors

At Inspiration Point, Yosemite, sticky whiteleaf manzanita tends to occupy south slopes, greenleaf manzanita tends to occupy north slopes. (Photo: NPS)

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As an avid hiker in Southern California, I’ve become a deep admirer of the chaparral that carpets so many of the hills and mountains in the region. When I was younger, I didn’t think much of these plants. They seemed dry, brittle, and uninviting, and they’d often leave nasty red scrapes on your legs if you ever ventured off-trail.

But I’ve come to respect them, not only because they’ve proven to be remarkably hardy, but because when you look closer, they reveal a kind of beauty I failed to appreciate when I was younger. I’ve written here and elsewhere about a few of them: the fascinating history of the toyon (Heteromeles arbutifolia), also known as California holly, which likely inspired the name Hollywood and is now officially recognized as Los Angeles’ native city plant; the incredible durability of creosote bush, featured in a recent Green Planet episode with David Attenborough; and the laurel sumac, whose taco-shaped leaves help it survive the region’s brutal summer heat.

Manzanita branches in the high Sierra. The deep red colored bark enhanced by water. (Photo: Erik Olsen)

But there’s another plant I’ve come to admire, one that stands out not just for its resilience but for its deep red bark and often gnarled, sculptural form. It’s manzanita, sometimes called the Jewel of the Chaparral, and it might be one of the most quietly extraordinary plants in California.

If you’ve ever hiked a sun-baked ridge or wandered a chaparral trail, chances are you’ve brushed past a manzanita. With twisting, muscular limbs the color of stained terra cotta and bark so smooth it looks hand-polished, manzanita doesn’t just grow. It sculpts itself into the landscape, twisting and bending with the contours of hillsides, rocks, and other plants.

There are more than 60 species and subspecies of manzanita (Arctostaphylos), and most are found only in California. Some stand tall like small trees as much as 30 feet high; others crawl low along rocky slopes. But all of them are masters of survival. Their small, leathery leaves are coated with a waxy film to lock in moisture during the long dry seasons. They bloom in late winter with tiny pink or white bell-shaped flowers, feeding early pollinators when little else is flowering. By springtime, those flowers ripen into red fruits: the “little apples” that give the plant its name.

Manzanita flowers (Santa Barbara Botanical Garden)

One of manzanita’s more fascinating traits is how it deals with dead wood. Instead of dropping old branches, it often retains them, letting new growth seal off or grow around the dead tissue. You’ll see branches striped with gray and red, or dead limbs still anchored to the plant. It’s a survival strategy, conserving water, limiting exposure, and creating the twisted, sculptural forms that make manzanita distinctive.

And fire is key to understanding manzanita’s world. Like many California plants, many manzanita species are fire-adapted: some die in flames but leave behind seeds that only germinate after exposure to heat or smoke. Others resprout from underground burls after burning. Either way, manzanita is often one of the first plants to return to the land after a wildfire, along with laurel sumac, stabilizing the soil, feeding animals (and people), and shading the way for the next wave of regrowth.

Manzanita’s astonishing red bark The reddish color of manzanita bark is primarily due to tannins, naturally occurring compounds that also contribute to the bark’s bitter taste and deter insects and other organisms from feeding on it. (Photo: NPS)

Botanically, manzanitas are a bit of a mystery. They readily hybridize and evolve in isolation, which means there are tiny populations of hyper-local species, some found only on a single hill or canyon slope. That makes them incredibly interesting to scientists and especially vulnerable to development and climate change.

Their red bark is the result of high concentrations of tannins, bitter compounds that serve as a natural defense. Tannins are present in many plants like oaks, walnuts and grapes, and in manzanitas, they make the bark unpalatable to insects and animals and help resist bacteria, fungi, and decay. The bark often peels away in thin sheets, shedding microbes and exposing fresh layers underneath. It’s a protective skin, both chemical and physical, built for survival in the dry, fire-prone landscapes of California.

Whiteleaf manzanita leaves and berries (Photo: NPS)

The plants still have mysteries that are being uncovered. For example, a new species of manzanita was only just discovered in early 2024, growing in a rugged canyon in San Diego County. Named Arctostaphylos nipumu to honor the Nipomo Mesa where it was discovered and its indigenous heritage, it had gone unnoticed despite being located just 35 miles from the coast and not far from populated areas. The discovery, announced by botanists at UC Riverside, highlights that unique species localization, as the plants are found sometimes growing only on a single ridge or in a specific type of soil. Unfortunately, this newly identified species is already at risk due to development pressures and habitat loss. According to researchers, only about 50 individuals are known to exist in the wild, making A. nipumu one of California’s rarest native plants, and a reminder that the story of manzanita is still unfolding, even in places we think we know well.

A new species of manzanita – *A. nipumu* – was discovered in San Diego County last year (2024), surprising reserachers. (Photo: UCR)

For hikers, photographers, and anyone with an eye for the unusual, manzanita is a cool plant to stumble upon. I will often stop and admire a particularly striking plant. I love when its smooth bark peels back in delicate curls, looking like sunburned skin or shavings of polished cinnamon. It’s hard to walk past a manzanita without reaching out to touch that smooth, cool bark. That irresistible texture may not serve any evolutionary purpose for the plant, but it’s one more reason to wander into California’s fragrant chaparral, where more species of manzanita grow than anywhere else on Earth.

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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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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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