Date: August 12, 2026
Place: Elkhorn Slough National Estuarine Research Reserve
Coordinates: 36.816789, -121.730461
Length: 3.8 miles
Level: easy
I have many posts in the pipeline but this, most recent hike I did, jumped to the top of the queue. It all started when Pappa Quail told me that the elder chika had asked him to take her on a whale watching boat tour. Inquiring into her latest desire I found out that she had received a school assignment to go out on a field trip and log any wildlife or signs of wildlife on that trip. After I was done being bummed about her not having asked me to go with her, I called and suggested that we'd go on a hike together. She still wanted a whale watching tour with her father, but she gladly accepted my invitation.
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| Our hike as captured by my GPS |
The Elkhorn Slough Educational Research Reserve has been on my wanna go there list for quite a while now. We've been there during the pandemic and had a great time canoeing up and down the slough. The reserve's land trails however, were closed at the time. Now I had the opportunity to go there with my daughter. It was cloudy and a bit chilly when we arrived at the reserve. Right away the chika made her first sighting - a turkey vulture in the gray sky.
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| Turkey Vulture |
The chika's next sighting announced its presence from a branch of a nearby live oak tree - a solitary crow that had some white spots on is black feather coat.
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| American Crow |
I was also making some sightings of winged creatures, but from a much much closer distance. A narrow traffic block that separated the parking area from the road leading to the visitor center was planted with gumplant bushes that were in full bloom. A crowd of insects were busy over many of the gumplant inflorescences.
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| Convergent Lady Beetle |
The first bee I actually saw was a gorgeous little bee with a bright green body. To my dismay, that bee flew away as I raised my camera, so I had to settle for less flashy, more common bee species.
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| Western Honey Bee |
We paid a short visit to the visitor center to ask which trail would be best for birding and other wildlife sightings. Outside the visitor center was a lovely little California native plants garden. The poppies in the garden were blooming nicely, and I spotted yet another wildlife species hiking on one of the poppy flowers' petals.
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| California Poppy, Eschscholzia californica |
Following the suggestion of the naturalist we started our hike on the Oak Trail behind the visitor center. The trail started as an accessible, flat concrete path that stretched between an area of dry weeds and a line of oak trees.
One of the oak trees really stood out with its drooping 'beard' of gray lichen. I love seeing this 'Treebeard' look on my hikes.
Interpretive signs along the way told us about the importance of the coast live oaks to the ecosystem of California coastal area. While I was busy reading the sign my chika spotted the first Mollusc on our hike - a large garden snail well attached to the the twig it was on.
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| Garden Snail |
I noticed a little pond a bit off the trail and motioned my chika to go there and check it out. An interpretive sign told us of the importance of that pond as a source of fresh water for the
amphibians, insects, and other animals in the area. The pond was covered with duckweed and we saw no waterfowl in it.
At the end of the line of oaks was one particularly large oak that stood a bit out. When we approached I noticed that what appeared to us as a single oak was was in fact three oaks with very close trunks and blended canopies. I suggested to my chika to go to the oaks and look closely at their trunks and branches.
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| Coast Live Oak, Quercus agrifolia |
In the past three months I was involved in a local biodiversity research project as a surveyor, looking for and photographing wildlife in native and non-native gardens around Santa Clara County. Through this project I became more aware of the places where invertebrates tend to be. I learned that many insects and spiders like living or hiding on tree trunks. A close inspection of these three oaks showed that to be true here as well.
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| Woodlouse Fly |
A short distance past the oaks was a small observation platform with binoculars, some interpretive signs, and a nice view to the slough.
Right by the rail of the platform grew a beautiful California coffeeberry bush. The bush (no relationship with actual coffee) had both flowers and maturing berries.
The rail of the observation platform right by the coffeeberry bush served also as a convenient perch for shiny looking fly.
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| Sedgesitter Fly |
A bit further away was a California wild rose bush, bearing one single flower. The flower was a bit too far for my camera but my chika with her birding lens got a nice image of this lovely beauty.
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| California Wild Rose, Rosa californica |
Just below the rail bloomed a few seaside daisy plants. Nice, new-looking spider webs stretched between the semi-succulent leaves and dark spiders were hanging upside-down on these newly spun webs.
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| Sheet-weaver Spider |
There were plenty of the Oregon gumweed shrubs by the rail as well, and all of them were in full bloom, providing an open buffet for many insects.
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| Oregon Gumweed, Grindelia stricta |
My interest in insects was, until fairly recently, mild at best. My interest was limited to the pretty-looking and/or functional relations with plants. In recent time my appreciation of these amazing little critters have grown exponentially.
It was after we left the observation platform that I realized I forgot to photograph the blooming seaside daisies. Oh, well. Past the observation platform the trail started descending downhill toward the slough. The trail, wide and white, was a great background for numerous dragonflies flying to and fro low over the gravel.
Both my chika and I spent the next ten minutes or so trying to photograph the dragonflies. That proved to be incredibly challenging. The dragonflies didn't fly particularly fast but they were not flying linearly. They kept moving up and down, left and right, in and out of focus. The photo below is the best I could do. My chika solved her problem by pulling out her phone and taking a video clip of these helicopter- like insects.
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| Wandering Glider Dragonfly |
A little lower along the trail the wetland started on the south. Tall bushes and dry weeds blocked at first most of our view but when there was an opening, I saw a large thicket of grayish-looking shrubs with tiny, semi-succulent leaves and tiny pink flowers. I was familiar with these alkali heath plants from other salt marshes in the Bay Area, but I'm used to seeing them rather small and flat. Here these shrubs were quite big.
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| Alkali Heath, Frankenia salina |
After descending some more we came upon the loop trail junction. On the left was the way directly to the slough and the right trail would take us first through an area of oak woodland before reaching the slough a bit further north. We decided to turn right into the oak woodland, and hike the loop in the counter-clockwise direction.
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| Coast Live Oak, Quercus agrifolia |
The oak woodland proved to be a rich habitat for many critters. One of the first that the chika pointed out was the gouty stem gall. A gall is a growth caused by an animal, in this case a wasp, that lays her egg inside the plant. The hatched larva secretes plant growth hormones that induce the host plant to form the growth. The wasp's larvae grow inside the galls, protected and surrounded by their food, until they pupate. The adult wasps then emerge from the gall to start once again a new life cycle.
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| Gouty Stem Gall Wasp |
The oak woodland was not very thick but spaced by areas of high bushes and brambles. Much of the bush area was dominated by poison oak, which I was careful to avoid.
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| Pacific Poison Oak, Toxicodendron diversilobum |
The bushes were ready for Halloween: spider webs covered them thickly. A human hand couldn't touch a leaf without tearing through cobwebs.
The insects, the intended prey, did have enough openings to slip through the spiderwebs. Some of these little bugs were really beautiful, too.
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| Wasp |
We saw the most wildlife species on a 50 feet stretch of trail in the oak woodland. Granted - nearly all of them were insects. Of all the insects I am posting here only a few selected photos - of the prettiest or most interesting ones (IMHO).
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| Western Calligrapher Fly |
It was only the two of us on that trail. Considering how many cars were in the parking lot I found that a bit odd. Perhaps everyone else went directly to the slough.
There were some flowers blooming along the trail. Not many, but some. The California hedgenettle added nice color to the dusty green of the bushes.
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| California Hedgenettle, Stachys bullata |
One of the things that impressed me most on the hike was the oak trees. These coast live oaks were old and very large. Their canopies were full and dark, and their boughs were heavy and twisted. Each tree was a unique work of nature's art.
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| Coast Like Oak, Quercus agrifolia |
There were little birds up those thick and dark oak trees. They were not easy to see, let alone photograph, but the chika practice good birder's patience and succeeded in documenting some avian wildlife.
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| Wilson's Warbler |
The Wilson's warbler I saw too - it was bright yellow. The vireo however, was a different matter. This tiny gray bird was very difficult to see in the dark oak tree. The chika succeeded in photographing this little cutie.
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| Hutton's Vireo |
My chika wasn't not looking only for birds. She spotted a cabbage white butterfly perching on a distant blackberry twig and pointed it out to me.
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| Cabbage White Butterfly |
I focused on the closer insects that I saw. Each of them another count on my chika's rapidly growing list of wildlife.
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| A Sawfly |
This time the bugs didn't avert my mind from the wildflowers. A nice black nightshade was showing the last of its flowers of the season. The plant was carrying mostly berries by now.
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| American Black Nightshade, Solanum americanum |
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| Gem-shaped Orbweaver Spider |
And then, not all spiders spin yarn and weave webs. Crab spiders are usually hard to see because they blend so well into their background. Here I spotted a ghost-white crab spider which really stood out on the deep green of the blackberry leaf.
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| Goldenrod Crab Spider |
I called my chika, who was very excited about this little find, taking a close up photo of this beautiful little spider.
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| Goldenrod Crab Spider |
We continued making a slow progress down the trail. A very slow progress I must say, because there was more and more wildlife to add to the list.
The chika head a bird call. She pulled out her phone and turned on her Merlin app to identify the caller. A warbling vireo it was. She spent some more time trying to spot the bird and eventually succeeded.
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| Warbling Vireo |
The vireo was hopping between the branches inside a thicket of arroyo willows that grew thick below the oaks where the oaks weren't too close together. Those willows proved to be yet another endless source of fascinating bugs.
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| Metallic Flea Beetle |
One of the beetle species we saw were actually willow leaf beetles. I caught some of them in the process of making even more willow leaf beetles.
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| California Willow Leaf Beetle |
I dare say that I never thought I would appreciate the beauty of a yellowjacket wasp. Having been stung by these vicious buggers I normally try to keep my distance. Now I was fearless in approaching them. They are in fact, quite beautiful.
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| Western Yellowjacket |
Eventually we extricated ourselves from the oaks and willows and moved on. We followed the trail sown to the water, the first part of which was a long and narrow lagoon that stretched inland from the slough's main channel. The cloudy sky reflected in the water, gray and gloomy.
There was another oak grove down the trail. This oak woodland however, while made of coast live oaks still, looked quite different from the oak woodland that we walked through earlier. This oak woodland had much less undergrowth below the trees. No willows or brambles or other bushes grew there, only grasses, which were dry at this time of year. The trees however, looked just as impressive with their sizes, canopy shapes, and long, artistically twisted boughs.
Even on the trail segments that were relatively free f trees there were some oaks showing an impressive presence. I simply love these trees.
I spotted some lupine bushes along the trail. Most of the lupines were done blooming and gone to fruit but one straggler still bore some late blossoms.
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| Coastal Bush Lupine, Lupinus arboreus |
The lagoon opened up into a larger expanse of water. I didn't see any waterfowl on the ripply surface, but the chika who was some distance ahead of me, exclaimed with excitement - she spotted a sea otter floating on its back.
I had to use my binoculars to see the otter, and the chika used her strong birding camera to take some photos. It was the first non-human mammal that we saw that day. The otter was tagged at it's webbed feet. I had no knowledge of what these tags meant - I've never seen a tagged otter before. I assume this particular otter was a known individual and that the researchers had a reason to follow its whereabouts.
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| Southern Sea Otter |
Shortly after seeing the otter we had our next exciting sighting. On the right hand side of the trail, under one large oak tree, was a small, human made tup, filled with duckweed-covered water. We've seen such a tub earlier on the hike - these tubs were constructed for the benefit of the endangered California red-legged frogs. We didn't see any frogs in the previous tub, but in this one we sure did.
These frogs are not easy to see, and there might have been more than one frog in that tub that were hiding a bit better. We were quiet and careful, and the frog, although aware of our presence, didn't dunk under the duckweed.
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| California Red-legged Frog |
There were some toyon bushes growing along the trail. Nearly all of them were at their green berry stage, but I did see some late season flowers blooming on one of them.
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| Toyon, Heteromeles arbutifolia |
The chika called my attention to one oak tree with low branches touching the ground. That oak was heavily parasitized by the gouty stem gall wasp. Nt a single twig or stem was free of the galls, and many stems carried several galls.
All the galls I saw on that tree were already vacant - sieved with exit holes. The tree itself seemed fine, not looking sick. I guess these oaks can bear the extra energy spent on these (best of current knowledge) free loader wasps.
The trail curved around another finger of the lagoon. Left of the trail we now saw many tall wild fennel plants. Fennel is an invasive species in California. Many creatures however, now rely on wild fennel as food source. I often see swallowtail caterpillars on wild fennel plants so I approached and looked closely. i didn't see any caterpillars, but did see many yellowjacket wasps roaming on the yellow umbel inflorescences. I retreated.
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| Fennel, Foeniculum vulgare |
Wild fennel is one plant that I enjoy munching on when it has fresh grown leaves. Near the fennel however, I saw one of its relatives that if consumed, would have killed me - the also invasive in California, poison hemlock.
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| Poison Hemlock, Conium maculatum |
Last season's fennel plants, dry but still standing, were an attraction for birds. The birds consume these plants' seeds. the elder chika spotted a common yellowthroat bird exploring these dry fennels.
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| Common Yellowthroat |
There was a thicket of willows on the right hand side of the trail. When we came upon an opening in the willows we saw a short trail leading to a water flow gate that connected the slough to a shallow, muddy pond. Naturally, we pulled off to explore that pond.
We didn't see any waterfowl or other water-related birds in or around the pond. The chika however, did find a cute little song sparrow in the weeds not far from where we stood. The sparrow was quiet, not living up to its name.
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| Song Sparrow |
Then the chika spotted a beautiful blue dragonfly, and both of us spent a few long minutes trying to get a decent photo of this pretty insect. My chika finally captured a beautiful image of it.
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| Blue-eyed Darner |
After giving up on getting a good photo of the dragonfly I turned my attention to a more stationary subject - the red bumps on the willow leaves that were the galls of the willow apple gall sawfly.
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| Willow Apple Gall Sawfly |
We returned to the trail and moved on along another inland cove of the Elkhorn Slough. The sky was still cloudy but the air was considerably warmer than when we started.
The warm temperature was just perfect for the lizards. We've seen many western fence lizards on this hike - the only representatives of the reptile order of animals we saw that day.
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| Western Fence Lizard |
When the view opened up to the slough past the oak trees we found our friend the sea otter again. It was the same individual, with the same blue tags and the same inquisitive looking face. It must have followed the same route that we did, on the water side of the coastline.
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| Southern Sea Otter |
Then we came upon a less pretty sight - the remains of a land mammal, later identified by the bones as a rabbit. The carcass was documented carefully by my chika as evidence of rabbit presence in the reserve. The bones of the deceased animal still had some flesh and fur on them, which attracted many a yellowjacket wasp and corpse flies. Not a pretty sight, but certainly natural.
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| Dead Rabbit |
Around the next curve of the trail there were three dead tree trunks that erected from the water near the shore. I scanned the dead and rotting trees with my binoculars and pointed out to the chika the woodpecker nesting hole.
Considering how many oak trees we've seen until that point I was surprised to not have seen or even heard the acorn woodpeckers. These colorful and noisy birds are quite common and usually make their presence known. Here we finally saw the woodpeckers, and from that point onward, we saw more of them along the hike. For whatever reason they seemed more quiet than I usually experience. Perhaps the gray sky subdued their usually chattery mood.
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| Acorn Woodpecker |
There were ferns growing under the living oak trees on that part of the trail. I checked the ferns, looking for insects but didn't find very many. I did see one pretty fly of a species that we didn't see yet earlier on the hike.
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| Thricops diaphanus Fly |
The trail curved again along the meandering shoreline of the slough. On our right hand side was a thick line of willow bushes to which a lower and redder thicket of poison oak was added. Through a gap in the willow we saw an inland lagoon of cam water, that appeared (judging by the vegetation) much less saline than the slough's water.
The north shore of the lagoon was dotted with waterfowl. We moved to a spot where we had a better view of the birds - they all turned out to be mallard ducks. Interestingly, we saw no other mallards anywhere else on our hike that day except for one flying pair high in the sky.
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| Mallard |
Right below us on the muddy shore of the lagoon stood erect a single great blue heron. The heron was well aware of our presence and eyed us suspiciously. The chika took some photos and we moved on.
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| Great Blue Heron |
I pointed an extended bare branch that hanged over the water and mentioned to her that that branch looked like it could be the perfect perch of a kingfisher bird. Shortly after the chika called out and raised her camera - a kingfisher was crossing the sky. She caught the bird's photo before it disappeared inside a far away knoll of oaks.
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| Belted Kingfisher |
The trail detached from the slough and rose above the water. Now we were walking through open grassland, with all the grass dead and dry.
Blue plants were blooming near the edge of the trail. These were chicory, a species introduced to California and established in the wild.
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| Chicory, Cichorium intybus |
There were morning glory flowers blooming too along that part of the trail. This species of morning glory is also non-California native.
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| Field Bindweed, Convolvulus arvensis |
The flowers added some color to the otherwise gloomy scenery, but they weren't the only being contributing color. Vibrant orange butterflies flew about us, occasionally taking rest on a twig here and there.
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| Mylitta Crescent Butterfly |
The attendant at the visitor center recommended two in and out trail spurs that went down to the slough ending in places where we could see more birds. The first one we came upon was the trail to Pelican Point, and we turned onto it.
A flock of little bush birds was active in the dry weeds. These birds were American goldfinches, and they were busy foraging on the seeds of the dry weeds.
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| American Goldfinch |
As expected, the birds didn't let us get too close to them. The did however, kept moving farther along the trail rather than flee sideways to the grass field. This happened every time we approached them. This dance kept happening again and again until the goldfinches finally decided it was enough, and flew behind us.
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| American Goldfinch |
Of the seeds that were available to whichever bird, rodent, or ants liked them were the seeds of the bristly oxtongue, yet anther invasive species in the California coast.
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| Bristly Oxtongue, Helminthotheca echioides |
The trail rose at a mild slope on the ridge of a flat topped hill. To the north we had a nice view of Pelican Point. A wide levee separated the inland lagoon from the main slough channel. We could see the trail extending northward on the levee.
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| Pelican Point |
When we got closer we could in fact, see pelicans resting on one of the low, flat islets in the inner lagoon. They were still quite far away but with my binoculars and with my chika's strong zoom lens we could see both white pelicans, typical of inland fresh water bodies, and Pacific brown pelicans, which are coastal, ocean birds. Here in the brackish water of the Elkhorn Slough their habitats overlapped.
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| Pelicans |
The chika became concerned about the time. We had planned to be at another place later that evening, and being all too aware of the rush hour traffic on Hwy1 she thought that we'd better pick up our ace. When I presented her with the choice between turning back right there and going down to the slough first, she chose to go down first.
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| Bird's-foot Trefoil, Lotus corniculatus |
There were also some native California plant species that were blooming, late summer flowers, such as the bird foot trefoil and the Pacific aster. Not carpets of bloom but lovely California wildflowers nonetheless.
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| Pacific Aster, Symphyotrichum chilense |
The inside lagoon was very calm. There were no waterfowl on the water but on the far away islet concentrated the pelicans as well as some gulls.
The chika pointed out the rippling circles in the water. They looked as if someone was throwing little stones into the water. These were in fact, little fish that were jumping out to catch the low flying insects. We saw their silvery flashes as the rose briefly over the water and fell back, rippling the surface. I put my camera on sequential mode and took I believe a hundred photos or so. None of the images show clearly any fish though. I chose to post the one that's closest to showing what we saw.
The trail continued north along the levee but the chica wanted to head back up the hill. Now she had the animal order of fish on her wildlife list.
We turn left to continue the loop trail, going closer to one slough's inland fingers that we saw from the ridge we waked on earlier. Far on the horizon we could see the two smoke stacks of the Watsonville power plant.
On a rotting pole in the salt marsh that flanked the slough perched a black phoebe bird, alert and ready to catch any insect that came into its field of vision.
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| Black Phoebe |
We moved southwest along the slough. On our left was the dry grass-covered hill dotted with occasional dark green bushes. On our right was a flat salt marsh that extended into the slough in a very nicely rectangular extensions. They looked very much like the remnants of some human-built operation but I didn't look into the human history of this place so I do not know what was their function. The elder chika kept looking for shore birds but so far didn't see any. It didn't help that the tide was high and most of the mud flats were still submerged.
We now faced the large lobe of the slough that we circumvented earlier on the oak woodland trail. The loop trail continued across the water on a low part levee part bridge. The structure allowed water under it, but functioned as a wave breaker as well - the inland part was much calmer.
The tide was receding at the time, but only a little bit of the mud was getting exposed. Still, there was much activity on the freshly exposed mud. The activity wasn't of shore birds though, but of shore crabs.
The chika was very excited. She (like myself) love seeing crabs. We spent a few long minutes looking at these beautiful and funny creatures. I pointed out to her that now she also had crustaceans on her wildlife list.
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| Striped Shore Crab |
On the other side of the bridge we came upon what looked like a weather station. It was an educational installation though, not an actual one. I noted it down as I did other educational signs along the way that had specific explanations of natura phenomena of the Elkhorn Slough area, and a QR code to follow for additional information.
Around the curve we saw a small metal bridge that connected the trail with one of the mud islets in the slough, not to far off shore. Behind that bridge was a beautiful shorebird - greater yellowlegs. The first shorebird that was close enough to take a good photo of.
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| Greater Yellowlegs |
A few people were standing on the observation platform at the end of the bridge. They carried binoculars and long-lensed cameras, sure signs that they were birders. My chika forgot all about the time constraints and walked right over there - they were her kind of people. I followed her slowly, taking in the expanse of the slough.
Just before the platform, as the bridge met the little mud islet, there was an exposed mud flat. A small group of least sandpipers was active on the mud, with a bit of foraging, and a lot of frolicking.
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| Least Sandpiper |
There were more interpretive signs at the end of the observation platform. While the chika got into conversation with the other birders that were there I took the time to look out and I spotted a solitary great egret on the far end of the islet. The chika later took its photo.
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| Great Egret |
She was also taking photos of shore birds that were present on other mud islets. Some of them were quite distant, but she was able to get good photos of them.
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| Marbled Godwit |
From that platform we also we had a good view of Hummingbird Island and the grove of dark, tall trees that grew there. I could discern oaks and Monterey pines but no more details.
Eventually the chika remembered that we were tight on time so we said goodby to the other birders and walked down the bridge back to the loop trail.
Below the bridge was a long strand of giant kelp. Giant kelp doesn't grow in the slough. Clearly it detached from its base in the ocean and got swept into the slough. Now it was caught at the bridge and I had a good chance to look at it closely.
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| Giant Kelp, Macrocystis pyrifera |
Back on the dry land trail I was looking again for wildflowers. The sticky monkeyflower bushes were sill in bloom.
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| Sticky Monkeyflower, Diplacus aurantiacus |
The few coyote brushes that were growing near the trail were also blooming still. Coyote brush has very unassuming flowers but when many bushes bloom together they can make quite an effect.
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| Coyote Brush, Baccharis pilularis |
This time I remembered to go up to the platform and take a photo of the blooming seaside daisies, which I missed on our first stop.
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| Seaside Daisy, Erigeron glaucus |
I thought that the chika would wait for me on the trail but she followed me up to the observation platform and found a skipper moth pollinating one of the seaside daisies,
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| Woodland Skipper |
We could have walked back along the original oak woodland trail but I saw that the asphalt road was leading to the visitor center as well and that the dragonflies we had so much trouble photographing earlier were now hovering over the pavement. I motioned the chika to take the road and made a few attempts to photograph the dragonflies. The chika didn't bother - she already had the video clip she took of the dragonflies earlier.
Back at the little botanical garden by the nature center I paused briefly to photograph a lovely willowherb plant that was blooming there.
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| Panicled Willowherb, Epilobium brachycarpum |
The elder chika called me and showed me the large interpretive sign that was standing at the end of the botanical garden. There was much information on that poster, and also an enlarged photograph of that gorgeous green bee that we saw near the parking lit when we first arrived and flew away before we could photograph it. We went back to that same patch of gumweed plants with renewed hopes, Indeed - that bee was there, and this time we did managed to photograph it.
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| Fine Striped Sweat Bee |
A monotonous clicking call came from the thicket of trees near the parking lot. It was a squirrel, and the chika went to look for it. The squirrel wasn't easy to find but she did find it - a second living mammal for her wildlife list.
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| California Ground Squirrel |
We finished the hike with many, many photos of wildlife and more. The chika definitely got her homework requirement fulfilled and both of us got to spend a lovely day together. That entire day the sun didn't break from the clouds, not even once.
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