Forest Clovers: Redwood Sorrel

When hiking in redwood forests, it’s likely that you’ve encountered redwood sorrel in the forest understory. A true shade-lover, redwood sorrel will fold its leaves when exposed to direct sunlight.

Places to See Redwood Sorrel

Cowell Circle

Henry Cowell Redwoods State Park

Redwood sorrel folds its leaves when exposed to direct sunlight.

When the leaves are in direct sunlight, they shrivel up and fold downwards within minutes. Sensitive cells in the plant detect the wavelength of light hitting it, causing the leaves to fold downwards when exposed to harsh light. This process is called nyctinasty.

Redwood sorrel’s folding is attributed to its sensitivity to bright sunlight. Because it is adapted to growing in low light conditions, intense light can damage the plant. Thus, folding its leaves is thought to protect it from harm.

To watch a time-lapse of this movement, check out this YouTube video. Please note that the plant shown is Oxalis triangularis, a different plant species in the same family as redwood sorrel.

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Redwood sorrel in bloom at Limekiln State Park in Big Sur, Ca.

Redwood sorrel is found on the West Coast of North America, from California to Canada.

It prefers understory habitats, often growing in coast redwood or Douglas fir forests beneath the shade of trees. It is one of the most common plants in the coast redwood understory.

Redwood sorrel leaves resemble clovers.

The leaves are 0.4 – 1.8 inches long. Redwood sorrel also has tiny (0.5 – 0.8 inch) flowers, which range from white to pink in color. Flowers can be seen in bloom from February to September.

Redwood sorrel is a good replacement for English ivy in a native plant garden.

Looking to make the conversion to native plants in your garden? Alternatively, are you looking for more native plants to introduce to your existing native garden? Consider the redwood sorrel. This plant grows well in shady conditions, forming a dense carpet beneath trees.

For more information on the planting and care of redwood sorrel in your garden, check out this article by S.F. Gate.

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Redwood sorrel at Henry Cowell Redwoods State Park in Santa Cruz, Ca.

Cool facts about redwood sorrel:

  • Redwood sorrel is truly adapted to shady environments, as it is able to photosynthesize in levels of light that are 1/200th of full sunlight.
  • The family name of redwood sorrels, Oxalis, is derived from the Greek word “oxys”, meaning sour. This is because the leaves of plants in this family have a sour taste.
  • Beware of eating too much of any plant in this family, as they contain oxalic acid. Oxalic acid can be toxic when consumed in large quantities.

Resources to learn more:

5 Ways Birdwatching Has Changed My Life

There are very few hobbies that I can say have changed my life for the better, and birding is at the top of that list. Here are just a few ways that birding has influenced me.

I have many hobbies that have enriched my life: reading, cooking, and dancing hula all come to mind as interests that make me feel happy and fulfilled. That said, there are very few hobbies that I can say have changed my life for the better. Here are just a few ways birding has influenced me.

1. Birdwatching taught me how to pay attention.

Birding has completely transformed my day-to-day activities by teaching me how to pay attention. While birding has allowed me to further develop my attention span, it has also taught me how to integrate nature into my day-to-day activities by simply paying attention.

Take walking from your parked car to a building as an example. Before I learned the sights and sounds of individual bird species, a walk from my car was just another task. Learning how to watch birds has flipped an irreversible switch in my mind, turning every moment outside into an opportunity to see or hear new things.

Today, even when doing something as simple as watering my plants outdoors, I passively pay attention to who’s around. Dark-eyed junco hopping underneath my gardening shelves, looking for spilled seed. House finch singing from a perch on the ornamental tree across the street. It’s an incredible gift that I’m grateful to have learned.

2. Watching birds got me to spend more time outside.

I’ve always loved the outdoors, but birding has presented me with the incentive to explore as many new habitats as possible, in hopes of observing more bird diversity.

Since I’ve begun birding, I’ve travelled to habitats ranging from rocky seashores to the edges of lush agricultural fields in search of a particular species. I’ve gotten to know a diversity of places, thanks to the journeys that birdwatching has brought me on.

Birding on the rocky shores of the Isles of Shoals, off the coast of Maine and New Hampshire.

3. Birds were a gateway to learning about other incredible wildlife.

Birds, like all other life, interact with a myriad of other species in their day-to-day activities.

As an avid birdwatcher, you sometimes can’t help but wonder who else is in the picture as you’re watching a particular bird. What kind of shrub is that California towhee scuttling under? What kind of plant is that song sparrow using as its singing perch? What kind of mammal did that red-tailed hawk just snatch up? 

These are common questions running through my mind as I watch birds, and are all musings that prompt me to jump on my computer once I’m back home to do some research. This cycle has led me to discover the names and life histories of many non-bird species, thus allowing me to become a more well-rounded nature lover.

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Shorebirds gather at the Palo Alto Baylands Nature Preserve.

4. Birdwatching has brought me to an amazing, tight-knit birding community.

Joy loves company, as proven time and time again in the friends that I’ve made through birding. Whether I’m living in the San Francisco Bay Area, upstate New York, or in the suburbs of Australia, there isn’t a single place that I haven’t found a tight-knit and supportive group of birdwatchers and nature enthusiasts. By joining local birding email listservs, local Audubon chapters, or even visiting a local nature center, I’ve met many new, welcoming faces.

5. Watching birds has allowed me to deepen my knowledge and involvement in local conservation issues.

Being a part of the birding community also meant joining forces with incredible advocates and leaders in environmental grassroots movements. Because of my involvement in the birding community, I’ve been able to learn more about important local conservation issues and projects that impact the habitats of native species.

In the Bay Area alone, I’ve been exposed to the wonders of wetlands restoration for native species, the declines of raptors such as American kestrels and burrowing owls, and the impacts that even a single crumb left behind at a campsite can have on the dynamic between Steller’s jays and marbled murrelets. While I would have likely read about these issues before becoming a birder, being an avid birdwatcher brings you that much closer to the battlefront of local conservation concerns.

(Bonus) 6. The excitement doesn’t stop at watching birds.

Birding has brought me happiness beyond just watching birds – it has allowed me to find other outlets for my passions, whether it be science education and outreach, science writing, photography, or travel.

Letting birds into my life has given me an incredible sense of purpose and belonging, and I can only hope that it will do the same in yours. Cheers to your next (or first!) birding adventure.

Me doing a bird banding demonstration with an American goldfinch to a group of young girls at the Cornell Lab of Ornithology’s Migration Celebration.

For more information on local bird species in the Bay Area, check out our wildlife resources on birds.

Logging, Crumbs, and Lost Fish: The Story of the Marbled Murrelet

Cover photo: © Tom Benson, 2014, some rights reserved.

Did you know that there’s a seabird that builds its nest high up in redwood trees? Learn about the marbled murrelet – from their breeding biology to what we think could be causing their population declines.

Cover photo: © Tom Benson, 2014, Flickr Photo Album, some rights reserved.

Quick Facts

  • Marbled murrelets are seabirds that venture inland to build their nests high up in redwood trees.
  • The health of coast redwood forests affects marbled murrelet populations, since murrelets need redwood forest habitats to breed.
  • Despite considerable conservation of redwood forests, marbled murrelet numbers are still declining by 4 percent annually.
  • Scientists have found that predation by Steller’s jays attracted to campgrounds by human food is affecting marbled murrelet numbers.
  • Since murrelets are seabirds, the health of our oceans could also be impacting marbled murrelet populations.


The Mystery of the Marbled Murrelet

Our story begins with a mystery.

Marbled murrelets are robin-sized seabirds that are closely related to puffins and murres. As is the norm for other seabirds, scientists expected the marbled murrelet to nest in large colonies along the rocky coast. Yet no such breeding colonies of marbled murrelets were found, despite the habits of their close relatives. The nesting place of the marbled murrelet remained an unsolved mystery to ornithologists in North America for over a century.

This changed in 1974, when a worker performing maintenance at Big Basin State Park discovered a lone nest high up in a redwood tree. The nest contained a single chick, which strangely had webbed feet. He snapped a photo that was later identified by bird experts as a marbled murrelet youngster. The mystery of the marbled murrelet nesting place was solved.

Defying all expectations of a seabird, these clever nesters fly 20 miles inland to construct nests high up in the cover of redwood trees. With this discovery, the marbled murrelet became the most recent bird species to have its nest found in North America.

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A coast redwood towering over the trail at Big Basin State Park, the site of the first documented marbled murrelet nest. Old-growth coast redwoods are the nesting sites of marbled murrelets.

Logging and the Loss of Murrelets

The California Gold Rush of 1848 brought steep human population increases to the San Francisco Bay Area – and with these population increases also came a huge demand for lumber. Settlers turned to the redwood stands along California’s coast for their supply. The irresponsible logging stripped most of the old-growth redwood forest from our coastline. It is estimated that only 5% of old-growth coast redwood trees survived logging.

Coast redwoods are critical to breeding marbled murrelets. Thus, the declines of redwood forests were closely intertwined to declines in marbled murrelet populations. The low murrelet numbers recorded off our coasts resulted in their listing as threatened under the Endangered Species Act in 1992. In California, they are state-listed as endangered.

The fate of the murrelets, along with other calls for the reduction of logging in the northwest, led to the 1994 Northwest Forest Plan under President Clinton. The plan protected 9.7 million hectares of old-growth forest along the coast of California, Oregon, and Washington.

Despite the protected breeding habitats, scientists monitoring murrelet populations still found that their numbers were declining. The population around California, Oregon, and Washington is continuing to decline by as much as 4 percent per year.

Crumbs, Jays, and Predation

A study at Redwood National and State Parks discovered one potential cause of the murrelet declines: predation by other birds, namely Steller’s jays.

Steller’s jays are crested blue and black birds found along the west coast of North America and south into Mexico. They are corvids, belonging to the same family as crows, ravens, and other jays. In addition to their diets of plant matter and insects, they will eat the eggs and young of other bird species.

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A common sign at campgrounds, featuring a Steller’s jay and a warning to clean up all traces of food. Source: Save the Redwoods League.

Steller’s jays are common at campgrounds, as their varied diet is supplemented by leftover food and crumbs from humans. These “crummy” areas attract jays and increase their density, thereby increasing the chances of Steller’s jays finding and predating the nests of marbled murrelets.

Public education programs are in place to decrease the amount of food left behind by humans. The initiative’s goal is to decrease the number of murrelet predators attracted to a given area. Signs are present in parks, warning people that food waste (even as small as a single crumb) has the potential to impact marbled murrelets.

Ocean Threats Still Loom

Scientists still don’t have all of the answers to what’s causing the murrelet population decline.

One factor affecting their numbers could be the availability of food off our coast. A study in Washington found that 80% of marbled murrelet nest attempts failed due to issues relating to low prey availability.

We do know that more frequent and intense El Niño events caused by climate change are negatively impacting fish populations. El Niño is a naturally-occurring phenomenon in which the number of upwellings of nutrient-rich cold water is reduced relative to “normal” years. Plankton, a main food source for fish, rely on the nutrients from the upwellings. With no plankton to eat, the fish populations (and the seabirds that depend on them) can be negatively impacted.

What does this mean for the marbled murrelet? Our efforts on land can be executed flawlessly, but the dual-lifestyle of this enigmatic seabird makes it so that their populations can still be harmed by threats to our oceans.

Stories such as these bring to light the importance of protecting as many diverse areas as possible. A holistic approach to conservation is necessary to save species that live such diverse lives.

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A view of the Pacific Ocean off the coast of California.


Sudden Oak Death’s Grip on California Forests

Oak trees have been in danger in California since the mid-1990’s, and researchers are now predicting a grim future for California’s emblematic tree. The killer, termed “Sudden Oak Death”, has killed an estimated 3 million trees since its introduction to California.

Quick Facts

  • Sudden Oak Death is caused by a fungus-like pathogen. It is fatal to many California-native oak species.
  • Since its introduction to California, the pathogen has killed an estimated 3 million trees.
  • Scientists have concluded that the pathogen’s spread in California is too great to completely eradicate it. Rather, management of the disease in localized areas is suggested to be our best option.


A Fatal Pathogen and Its Spread

Something weird began happening to California’s oak trees in the mid-1990’s.

Trees were plagued with a sudden onset of dying leaves and trunks that “bled” dark-colored sap, and locals concerned about the sudden tree deaths reported their observations to specialists.

The pathogen causing the symptoms was identified in 2001 as Phytophthora ramorum, a fungus-like species that infects plants. P. ramorum arrived to California by infested rhodendron plants. The fungus spread across the United States through shipments of nursery plants before it could be detected. It is spread through spores, which can be carried by rain, wind, and infected soil.

The symptoms exhibited by infected plants vary by plant species. Some plants can be infected with the pathogen and not have symptoms serious enough to be fatal, allowing the plants to continue living and spread spores from the pathogen as “carriers”. The California bay laurel is a well-known carrier, since its symptoms are limited to spots on some parts of the leaves and diebacks of twigs.

P. ramorum is known to cause death in a number of oak species, including coast live oak, Shreve oak, and California black oak. P. ramorum is also known to infect a relative of oaks, the tanoak. The main symptom of infected trees is a canker on the trunk, with blackish to reddish sap that “bleeds” from the sore. Infected trees take an estimated 2 years to die from the pathogen itself; however, other pathogens and insects readily infect the already-sick trees and speed up the tree’s death.

A Disease With Far Reaches in California

Since its introduction to California in the mid-1990’s, Sudden Oak Death has killed an estimated 3 million trees along the coast from Big Sur to Oregon. The effects of this disease also go beyond just the deaths of trees – trees that have died from Sudden Oak Death are dangerous fuels for California wildfires, a threat that has become more prominent as we face the effects of climate change.

Management practices have focused on the identification, quarantine, and removal of infected plants as a way to stop its spread. Public education initiatives have also focused on educating California residents on how to avoid spreading the disease, through practices such as sterilizing pruning tools and washing off equipment, tires, and shoes that have come in contact with infected soil.

Predicted spread of the sudden oak death epidemic through California, 1990–2030
An image from Meentemeyer et al. 2011 showing the predicted spread of Sudden Oak Death from 1990 – 2030, based on the assumption of similar weather conditions to those in California from 1990 – 2008.

Despite California’s efforts, a recent study (Meentemeyer et al. 2011) conducted by scientists from Cambridge, the University of California at Davis, and the University of North Carolina has concluded that completely eradicating the disease from California is not possible. The sheer number of trees infected makes it impossible to rid the state of the disease or stop its spread.

Instead, the study suggests that management should focus on the restoration and treatment of small, local forests as the most practical and cost-effective option. One such study focusing on removing dead and diseased trees is currently being conducted around Bolinas Ridge, giving us hope for the development of best management practices moving forward.


The Bay Area’s Fight for the Western Burrowing Owl

Cover photo: © Nathan Rupert, 2010, some rights reserved.

Learn about the burrowing owl’s current conservation status in the Bay Area and the current initiatives to protect them.

Cover photo: © Nathan Rupert, 2010, Flickr Photo Album, some rights reserved.

Quick Facts

  • The western burrowing owl is a small species of diurnal owl, meaning that it’s active primarily during the day.
  • The burrowing owl used to be common in the Bay Area, but habitat loss has caused a steep decline in their populations over the last 30 years.
  • Local conservation groups are working to improve habitats to make them more attractive to owls, and are working on monitoring sites known to have owls.


Nestled on the edge of a corporate development next to the entrance to a local wildlife preserve lies a small, fenced-off lot of short grass. Here, after minutes of scanning small mounds of dirt, Dan and I encountered our first burrowing owls. An adult sat hunkered down, directly next to a young owl that was curiously peering back at me with large, yellow eyes. With this developed backdrop, it is difficult not to question the fate of this charismatic species.

A Bay Area Species in Peril

The western burrowing owl is a diurnal owl, meaning that it’s active during the day. It’s fairly small, standing at about 10 inches high. True to their name, they nest and reside in burrows in the ground – relying on sites that have already been excavated by burrowing mammals such as the California ground squirrel. They can often be found standing vigilant outside of their burrows during the day.

This endearing bird was once a common bird in the South San Francisco Bay Area. In the mid-1980’s their population was estimated to be about 640 individual birds – with three-quarters of the population residing in the South Bay alone. Today, their population has been reduced to isolated breeding and overwintering populations (overwintering populations migrate to the Bay Area during the winter to escape cold temperatures in their other homes). In 2017, the South Bay reported just 64 adults at 5 breeding sites.

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An adult and juvenile western burrowing owl in the South Bay.

Habitat Loss and Evictions

Habitat loss is the main threat that these owls face. The South Bay was once host to native grassland habitats; however, housing and other commercial developments to address a booming human population have outcompeted the owls for space. The East Bay is facing similar problems – areas that overwintering owls need to be successful have rapidly disappeared, putting stress on their populations.

Even at sites where the owls reside, the active removal of burrowing owls takes place. Developers that are initiating projects at known burrowing owl sites will hire contractors to install one-way doors at burrowing owl sites – allowing the owls to leave their burrow, but not to re-enter.

These “evictions” are rendered legal because individuals or nests are not harmed. However, many groups criticize the practice since there is no monitoring of the evicted birds after the traps are installed. Burrowing owls have high nest site fidelitymeaning that they have high rates of returning to the same breeding site, and even specific burrow, year after year. With the evictions taking place without long-term monitoring of the displaced owls, the effects of practices such as these are unknown and the evictors are not held accountable.

Bay Area Organizations Band Together for Owls

Efforts to increase the population of breeding burrowing owls in the South Bay are currently being implemented. A number of South Bay organizations have banded together to increase the population of breeding owls at Warm Springs in Fremont. Based on the outcome of their efforts, they will apply what they’ve learned at this site to the management of other sites in the South Bay. Similarly, the Santa Clara Valley Audubon Society is working in Alviso, a neighborhood in San Jose, to provide suitable habitats for the owls. The group works to install artificial burrows and mow the area to keep vegetation short.

In the East Bay, the Golden Gate Audubon Society, the City of Berkeley Marina and the Shorebird Nature Center have joined forces to create the Golden Gate Audubon Burrowing Owl Docent Program. The program focuses on raising public awareness about keeping dogs on-leash to help protect the overwintering owls that use the areas in the East Bay. Docents also keep track of the burrowing owl numbers in their area – allowing for long-term population data.

Efforts such as these provide hope for burrowing owl populations, yet their fate is still undecided in the face of the rapidly expanding Silicon Valley.

For more information on how to volunteer for the Golden Gate Audubon Society’s Owl Docent Program, please visit this page and scroll to “Train to Become a Docent” towards the bottom of the page. For more information on volunteering with the Santa Clara Valley Audubon Society doing habitat restoration at Alviso, please visit this page.


The Brown Recluse: How Dangerous Is It?

Cover Photo: © Andrew Hoffman, 2012, some rights reserved

Recluse spiders are some of the most feared spiders in America. Rumors of infestations, highly dangerous bites, and even deaths have spread throughout the country. Yet despite the rampant arachnophobia, brown recluses are actually not so dangerous when we take a closer look at the spider behind the hype.

Cover Photo: © Andrew Hoffman, 2012, Photo Library, some rights reserved.

By Dave Frank, Contributor

Recluse spiders are some of the most feared spiders in America. Rumors of infestations, highly dangerous bites, and even deaths have spread throughout the country. Yet despite the rampant arachnophobia, brown recluses are actually not so dangerous when we take a closer look at the spider behind the hype. Let’s explore some common myths and misconceptions about the brown recluse!

Myth #1: Recluse bites are extremely dangerous!

First, we need to address the rates of spider bites in general. There are many myths about spider bites. One common myth is that you can tell a spider bite from another bug bite, such as a mosquito bite, because a spider bite will have two puncture wounds while a mosquito bite will only have one. While it is true that spiders bite with two fangs, in contrast to the bite of a mosquito’s single mouthpart, spider fangs are usually too small and close together for us to actually see both bite marks. A spider bite would appear as a single wound, much like a mosquito bite. In fact, mosquitos are responsible for far more deaths worldwide than spiders.

According to Rainer Foelix’s Biology of Spiders, “only four genera are known to cause potentially deadly bites.” Loxosceles reclusa, the American brown recluse, is one of these spiders, but most recluse bites are harmless. The venom of spiders is used to paralyze their prey, so bites on humans would only be defensive. And this is a rare case, as recluses (as with most spiders) are not aggressive towards humans. They are actually much more scared of us than we are of them!

Their bites are necrotic, which means that their venom causes tissue degeneration at the site of the bite. This is different from spiders such as the black widow, Latrodectus mactans, which have neurotoxic venom. Neurotoxic venom will cause nerve damage and paralysis to prey. For humans, the bite of a recluse is very unlikely to lead to significant injury or death. We are much larger than their usual prey, so their bites do not contain enough venom to hurt us much. As long as one seeks medical attention for wounds causing pain or that won’t heal, recluse bites are survivable.

Myth #2: Brown recluses are common in California!

In America, the range of the brown recluse is contained mainly in the southern states. While there have been sightings in California, these are extremely rare. In fact, an entomologist at University of California, Riverside argues that there are no populations of brown recluses in California. Rick Vetter states that hundreds of spiders have been brought to the entomology department at UC Riverside for identification, and not a single one was a brown recluse.

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Recluse Range Map, taken from UC Riverside Entomology Department,

The map above shows the common ranges of recluse spiders in the U.S. Loxosceles reclusa is the species of brown recluse with bites that are the most medically significant. As you can see, their range does not extend west into California. While other recluse species can be found in California, these species do not have bites that are medically significant. Loxosceles deserta, the desert recluse, can be found in California, but they live far from urban areas and so are not considered dangerous due to their extremely limited interaction with humans.

Myth #3: Recluses are aggressive spiders!

As stated previously, recluses are not aggressive. There’s a reason they’re called “recluses” after all! Recluses like finding hidden spaces to build their nests. Older homes can be perfect habitats for them, but they often coexist peacefully with humans. As far as infestations go, there are many reports of recluses being found in large numbers. However, most of these events are blown out of proportion. In Brentwood, TN, a woman claimed to have been bitten several times due to an infestation in her apartment. However, the articles do not always have scientifically accurate information and may be misleading. For example, the main picture of “brown recluses” in this article does not show a brown recluse, as the spider shown is not even brown! While recluses can be found in high numbers in suitable locations, it is extremely rare for them to interact negatively with humans.

Myth #4: Brown recluses are difficult to tell apart from other spiders!

Brown recluses are quite easy to identify. The most telling feature of a recluse is the pattern of the eyes. Most spiders have eight eyes arranged in two rows. Recluses have only six eyes, and these are arranged in three pairs across the cephalothorax (head and torso region). They also have a violin shaped pattern along their backs, which is why they are sometimes called “fiddleback spiders”. Recluses are around ⅜ of an inch in length, a little smaller than a penny, and are have uniform brown coloration. Other spiders may have some of these aspects, but if a spider you are trying to identify does not have these characteristics, then you have not found a brown recluse.

Brown Recluse Spider
© Andrew Hoffman, 2012, Photo Library, some rights reserved

For those who may still be arachnophobic, please take a look at this video! This person is holding a brown recluse and a black widow, the most commonly feared spiders, in one hand. As you can see, neither spiders attack the cameraperson. These spiders are actually rather mild-mannered. We do not recommend trying this at home, but hopefully it shows that humans have very little to fear from our eight-legged friends.