Palo Alto, California

Site 1: Stevens Creek Shoreline Nature Study Area

Site 2: Charleston Slough, Adobe Creek, Shoreline Lake

Site 3: Baylands Nature Preserve

May 19, 2023

9:30 am to 3:30 pm

It was a sunny day with a high of 72° F.

An estuary is where two bodies of water with differing chemical make-ups come together and mix. At the Baylands, the freshwater flowing down the watershed meets the saltwater flowing into the bay from the ocean. The freshwater flows from the mountains through water channels such as rivers, creeks and underground. In the Lower San Francisco Bay, the ocean water flows under the Golden Gate Bridge into a wide but enclosed body of water. Then, the magic happens where we see the estuary form through the mixing of salt water and freshwater.

Major adaptations of the plants focus on surviving in a salt-water environment. Salt grass has specialized cells that secrete salt. Pickleweed concentrates the salt into the extremity of the plant and then turns red and falls off. Because Cord grass can be fully submerged in the water, it has hollow tubes from leaf to stem to supply oxygen. The photosynthetic plankton such as diatoms and algae, salt grass, pickleweed, and cord grass are the major primary produces of this ecosystem. This estuary is incredibly productive because the mixing of nutrients deposited from the watershed goes into the system where light can penetrate the entire water column. An exciting process connected to climate mitigation efforts is that the seagrasses and salt marshes of estuaries are able to sequester significantly more carbon than terrestrial systems.

Saltmarsh dodder is a parasitic plant that can commonly be found growing on pickleweed. It is composed of long and twisting orange stems. From the stems, dodder penetrates the cell wall of green plants to obtain nutrients with rootlike structures called haustoria. Because it is parasitic and obtains its nutrients from other plants rather than going through the process of photosynthesis, it does not grow leaves. It does, however, flower in order to reproduce. If you look closely at the photo above, you can see that the dodder is in bloom with a couple of small white flowers.

There were extensive cliff swallow nests built along the inner roof of the Baylands Nature Preserve Visitor Center and under the neighboring viewing bridge. Cliff swallows build mud nests with cavities and the babies can often be seen with their heads poking out. The nests were full of babies with parents busily flying back and forth to feed them. Cliff swallows have fanned tails and a white stripe above their beak. Climbing up the side of the building, we observed a gopher snake on a mission of predation. Gopher snakes will travel from nest to nest, eating eggs and babies. Another predator about was a raven, whom the swallows mobbed in a failed attempt to chase it away.

There is also a healthy population of barn swallows throughout the Baylands. Barn swallows also build nests from mud which are found on roof overhangs and under bridges. Their nests have a characteristic open cup shape rather than the cavity nest that cliff swallows build. One way to distinguish barn swallows while in flight is through the characteristics of their tail. Barn swallows have long, heavily forked tails with white spots. This is why their hunting flights are a joy to watch, with their dives and swirls in the air like an acrobatic performance.

A delightful bird to watch hunt for fish are terns. We observed one tern that seemed attached to standing at the shoreline, loudly calling to the other terns flying through the sky. I wondered at the time if it was a younger bird begging the parents to share a meal. When terns hunt for fish, they rapidly flying through the air scanning the water. When they see an opportunity to catch a fish, they dive straight down into the water to grab it. If you look at the center of the photo above, you can see a tern pointed straight downward, about to hit the water. There must have been quite a bit of fish in that area of Shoreline Lake, because we came upon several bird species energetically, and successfully, hunting for fish. One cormorant was busy diving, fully emerging under the water, and popping up its head with a small fish in its mouth. A snowy egret was also in on the action, not paying any mind to the chaotic energy around it.

In the same area where the terns, cormorant, and snowy egret were feasting, we found an abundance of crabs. We found crabs as small as our fingernail tip and large enough to fit in the palm of our hands. They moved quite quickly, probably due to the many migrating and breeding birds that were happy to take them on as their next meal.

A sad moment of the day included witnessing the quiet emptiness that can follow the colonization of an invasive species of plant. The species itself may thrive, but the habitat that supported the lifecycle of local species ceases to exist. The landscape pictured above used to be dominated by cattails, which happened to be the preferred habitat for red-winged blackbirds to nest. Many years ago, our professor shared that the skies were filled with mating red-winged blackbirds. That day, we did not observe any red-winged blackbirds in the area, nor generally any birds in this particular spot. The driving force behind this moment of silent spring? Arundo, or giant reed, has completely colonized the area.

The native habitat of arundo is in India but has become an incredibly invasive plant in California and other southern states. It was originally planted in California in 1840 for erosion control and to use for building material. At the present, it is recognized that it aggressively colonizes riparian and wetland ecosystems, outcompetes native plants and therefore degrades fish and wildlife habitat, consumes vast amounts of water, increases fire risk, and creates erosion and flood control issues. It is extremely fast growing. Arundo can achieve four inches of growth in a day and has the capacity to mature to 20-30 feet in a year. The stems resemble bamboo while the leaves have a similar look to corn.

Arundo propagates through rhizomes (a horizontal underground stem that sends up shoots) or through new roots forming at the nodes when a piece of stalk breaks off. Part of the way that it heavily colonizes waterways is that as pieces brake and flow downstream, new colonies form. There was an attempt in the area of the photo to manage the arundo through cutting it down. Unfortunately, that just stimulated more growth.

I would be remiss to describe the effects of an invasive plant on the area without sharing the large investments in restoration efforts that have created heartening and effective results. One of the restoration actions included breaking a levee and allowing the water to re-enter an area. To the surprise of many, the area recovered in only a couple of years! This is an exciting area to watch and hopefully learn from in terms of restoration efforts.

Glossary of Scientific Names

Salt Grass: Distichlis spicata

Pickleweed: Salicornia

Cord grass: Spartina

Saltmarsh dodder: Cuscuta salina

Arundo: Arundo donax