Science Spotlight

The automated recorder model the scientists used. (CDFW photo by Brett Furnas)

Two avian researchers recently completed a groundbreaking study on the effects of climate change, based on the calls of California’s songbirds. By recording the sounds made by eight different songbird species, and tracking the dates they are most vocal and how frequently they sing, the scientists were able to develop a method to measure how the birds are adjusting to climate change.

CDFW Wildlife Ecologist Dr. Brett Furnas and William Jessup University’s Professor Michael McGrann analyzed data from two bird surveys, one done by CDFW and another led by William Jessup University, in the Klamath Mountains and Southern Cascades of northern California. Both studies used automated recorders to monitor bird sounds between 2009 and 2011. The results of their analysis, detailed in a research article entitled Using Occupancy Modeling to Monitor Dates of Peak Vocal Activity for Passerines in California, were published this month in a peer-reviewed, international journal of ornithology, The Condor: Ornithological Applications.

Furnas and McGrann’s study was prompted by the scientists’ concern that climate change could throw bird’s reproduction cycles out of sync with the seasons. Their work, which represents the first comprehensive assessment of songbird occupancy over approximately 15,000 square miles in California, earned high praise from Steve Beissinger, an expert on avian phenology at the University of California, Berkeley.

“Furnas and McGrann provide a textbook example of how to detect differences in the timing of nesting among bird species using information on the peak date of singing derived from surveys and automated recorders,” Beissinger said. “Their results support recent findings of a five-to-twelve day shift forward in the timing of peak singing by California birds in the nearby Sierra Nevada and coastal ranges in response to climate change.”

Because birds’ songs are correlated with their breeding behavior and are easily identifiable to species, the scientists found them to be a useful tool to provide new baseline data for the birds of northern California. Working together, they identified the precise dates of peak vocal activity for eight songbird species: Hutton’s vireo, hermit thrush, dark-eyed junco, Nashville warbler, MacGillivray’s warbler, yellow warbler, western tanager and black-headed grosbeak. In addition to gathering baseline data, Furnas and McGrann developed a method to track advances in the timing of vocal activity in the coming decades.

Male songbirds sing for several reasons -- including to advertise their territory or to find a mate with which to breed. When birds are at their most vocal, they are usually near the height of their breeding season, Furnas explained.

Much like the call of the imperiled “canary in the coal mine,” changes in the frequency or timing of these native birdsongs can serve as barometers of the cumulative impact of climate change.

“When the canary starts singing you know that there is a danger, such as a buildup of dangerous gasses in a mine,” Furnas explained. “When the birds in our study start singing earlier in the season, they are warning us that climate change is starting to disrupt complex ecological cycles that developed slowly over millions of years of evolution.”

One of the most interesting findings of the study so far is a hint in the baseline data that migratory birds may be at greater risk than non-migratory birds. “We found the highest singing activity for migrant birds spanned a shorter number of days than the highest singing activity for non-migratory birds,” Furnas said. “This could be because migratory birds have less flexibility to shift the timing of their breeding cycle. If they are prompted by increasing temperatures to migrate earlier in the year, they may arrive at their breeding grounds to find they don’t have enough insects to eat.

“Migratory birds have to compress a lot of activities into a shorter time period with less margin for error,” Furnas explained. “Think of it like scheduling a short holiday somewhere nice, but when you show up, bad weather cancels out a lot of your itinerary.”

This, in turn, negatively affects the very biodiversity that CDFW is responsible for monitoring.

“If all the species adjusted their ecologies similarly, perhaps that would be OK, but unfortunately, we expect that different insects and birds will react in different ways leading to a mismatch of conditions,” Furnas said.

Both CDFW and William Jessup University plan to continue bird surveys over the long term so that California has the information to support effective management of climate change and other conservation challenges.

Top photo: Singing hermit warbler, one of the species addressed in the study. (CDFW photo by Michael McGrann)

Staff of several wildlife agencies carry light-footed Ridgway’s rails (previously known as light-footed clapper rails) to Batiquitos Lagoon Ecological Reserve.


A light-footed Ridgway’s rail is banded before release into Batiquitos Lagoon Ecological Reserve.

The Ridgway’s rail is a grayish-brown, chicken-sized bird with a long, downward curving bill and a conspicuous whitish rump. Previously known as the clapper rail, the species name was changed in 2014 to honor ornithologist Robert Ridgway. Three subspecies of Ridgway’s rail are resident in California, all of which depend on mudflats or very shallow water (wetland habitat) where there is both forage and taller plant material to provide cover at high tide. They rely on marsh plants such as cordgrass and pickleweed for breeding and feeding.

One subspecies, the light-footed Ridgway’s rail, was once abundant in the Southern California wetlands, but fell to near extinction in the 1980s as their historical habitats were displaced by housing developments. Today, they have a chance to repopulate, buoyed by recent wetland restoration projects by the California Department of Fish and Wildlife (CDFW) and “Team Rail,” a group that has been dedicated to the recovery of this federal- and state-listed marsh bird for more than a decade.

Team Rail is comprised of scientific staff from CDFW, the U.S. Fish and Wildlife Service (USFWS), the U.S. Navy, three zoological breeding centers (SeaWorld San Diego, the San Diego Zoo Safari Park, and the Living Coast Discovery Center) and the Huntington Beach Wetlands Conservancy. Thanks to their efforts, the 2017 rail population reached 514 pairs in the wild. Each rail release is a step closer to achieving the 1985 Light-Footed Clapper Rail Recovery Plan objective of having 800 breeding pairs in California.

Most recently, five light-footed Ridgway’s rails were released into the Batiquitos Lagoon Ecological Reserve in San Diego County. This release consisted of two mated pairs and three offspring produced by one of the pairs. Three of the adults are retired breeders from the zoological breeding program and are part of a rotation plan to reintroduce retired breeders back into the wild. The release of these individuals will contribute genetic diversity to this highly endangered marsh bird population. Rails bred in zoological facilities were released into Batiquitos Lagoon in 2004 and 2005 (eight rails each year), in 2013 (six rails), 2014 (12 rails), and 2015 (seven rails).

“Given that State Ecological Reserves are set aside for the conservation of threatened, rare and endangered species, and rail releases are targeted for wetlands with small subpopulations (fewer than 50 breeding pairs), Batiquitos Lagoon is an ideal location for the release of Ridgway’s rails,” explained CDFW Senior Environmental Scientist (Specialist) Nancy Frost. “For over a decade, CDFW has supported numerous research and monitoring projects for this species, and we are proud to be a partner in their recovery.”

The state-owned Batiquitos Lagoon is managed by CDFW and is one of the few remaining tidal wetlands on the Southern California coast. Located in the city of Carlsbad, it consists of 543 acres with a drainage basin of about 55,000 acres. It is home to several threatened and endangered birds, insects, plants, fish and mammals and is also designated as a State Marine Conservation Area under the Marine Life Protection Act.

Top photo: A light-footed Ridgway’s rail flies away after being released at Batiquitos Lagoon Ecological Reserve in San Diego County.

Kerstin Wasson is leading the Olympia oyster restoration at Elkhorn Slough. Kerstin Wasson photo.


Scientists are working hard so that a new generation of Olympia oysters may one day line the mudflats at the Elkhorn Slough Reserve.


Volunteers Ken Pollak and Celeste Stanik join Dr. Chela Zabin to improve the native oyster habitat at Elkhorn Slough. Kerstin Wasson photo.


Suspended gaper clam shells hang in aerated laboratory tanks, home to what scientists hope will be a new generation of Olympia oysters at the Elkhorn Slough Reserve.


Graduate student Dan Gossard, at CSU’s Moss Landing Marine Laboratories, shows off one of the clam shell “mobiles” on which the Olympia oyster larvae will attach when suspended in aerated tanks.


Kerstin Wasson points out Olympia oysters along the banks of the Elkhorn Slough Ecological Reserve in Monterey County.

For the first time in California history, scientists are turning to shellfish farming techniques to restore native oyster populations.

The groundbreaking research is taking place with Olympia oysters at CDFW’s Elkhorn Slough National Estuarine Research Reserve in Monterey County, in partnership with the California State University’s nearby Moss Landing Marine Laboratories and its new Center for Aquaculture.

Olympia oysters and other shellfish were once so abundant at Elkhorn Slough that Native Americans living there had multiple processing centers along the estuary’s banks to handle their harvest. Olympia oysters have disappeared altogether from many places along the California coast and their numbers at Elkhorn Slough have dwindled so low – estimated today at just a few thousand oysters – that scientists fear they may no longer be able to reproduce in the wild. Not since 2012, they say, have Elkhorn Slough’s wild oysters produced any offspring.

A combination of factors is believed to have caused the population drop over time, including poor water quality because of agricultural runoff from nearby farms and alterations to the landscape and tidal flow from generations of farming and other human activity prior to the area becoming protected in a series of conservation purchases beginning in 1971. An infusion of freshwater from last year’s rainy winter caused a severe oyster die-off and spurred biologists into action.

“This is an iconic species in our estuary in danger of disappearing,” said Kerstin Wasson, Research Coordinator at Elkhorn Slough, where she has worked for 17 years with funding from the National Oceanic and Atmospheric Administration (NOAA), the federal partner in the Elkhorn Slough Reserve. “These oysters fed native people here for 7,000 years.”

In late August, dozens of Olympia oysters were gathered and brought to the Moss Landing Marine Laboratories, where 20 spawned successfully. A few hundred thousand of their microscopic offspring are now swimming in large, circular laboratory tanks and attaching themselves to gaper clam shells suspended on fishing line from the top of the tanks. The clam shells bearing young oysters will be bound together into makeshift reefs and returned to Elkhorn Slough early in 2018 to bolster the native population.

The research is being led by a small group of scientists, including Wasson and graduate student Dan Gossard with funding provided by the Palo Alto-based Anthropocene Institute. These are uncharted waters for California scientists, however, and a major assist is coming from the aquaculture industry itself. Peter Hain of the Monterey Abalone Company has worked closely with the two researchers to set up the laboratory facility for the Olympia oysters and help with their care and feeding.

Due partly to their small size – an individual Olympia oyster is about the size of a 50-cent coin – and slow growth, Olympia oysters hold little appeal and little potential profit for most commercial oyster farmers who focus on larger Pacific varieties, many native to Japan. Taylor Shellfish Farms in Washington State is the only known commercial producer of Olympia oysters.

Wasson welcomes interest and support from aquaculture and hopes growers might one day add the native oyster to their operations. She believes even a niche commercial market for Olympia oysters could have positive implications for wild populations, enhancing recruitment, broadening scientific knowledge and a general appreciation for the native mollusk by the public.

Other efforts to save wild oyster populations in California and elsewhere have focused on building jetty-like artificial reefs constructed from oyster shell contained in plastic mesh.

Wasson prefers that more natural materials be used as part of the oyster restoration efforts underway at Elkhorn Slough, creating small clusters of oysters rising above the mudflats.

“I want this place to look like it did 200 or even 2,000 years ago,” she said.

Top photo: A huge influx of fresh water during winter 2017 resulted in an Olympia oyster die-off and spurred biologists into action.

A California red-legged frog sits motionless at the edge of McClure pond at the Sparling Ranch Conservation Bank. Photo by Ashley Spratt/USFWS


McClure pond is one of the most productive California red-legged frog ponds at the Sparling Ranch Conservation Bank. Like many of those on Sparling Ranch, it was named after the family who homesteaded in site in the late 1800s. Photo by Ashley Spratt/USFWS

Since the mid-1980s, California has been using a system of conservation and mitigation banking to protect valuable natural resources and critical habitat for fish, wildlife and plants. These banks are generally large, connected, ecologically meaningful areas of preserved, restored, enhanced or constructed habitat (for example, wetlands) that are set aside for the express purpose of providing mitigation for project impacts. Conservation banks provide mitigation for impacts to listed species and habitats, while wetland mitigation banks primarily provide mitigation for wetland impacts. Together, they serve to prevent inadequate, fragmented reserves that can result when mitigation projects are carried out individually.

Banks work by establishing credits for sensitive species or habitats found on a given site. These credits can then be sold to developers or other project proponents who need to meet permitting requirements or are otherwise required to compensate for environmental impacts. For those parties needing to mitigate for project impacts, banks serve to streamline the regulatory process by providing a pre-established mitigation site that the regulating state and federal agencies have already confirmed will provide adequate and appropriate mitigation for certain habitats or species. By mitigating at a bank, project proponents can avoid the time and cost of searching for a suitable mitigation site and protecting it in perpetuity themselves.

In order for the banking system to be effective, state and federal agencies must work closely together to align processes and practices. Since 1993, CDFW has been participating in the planning, review, approval, establishment, monitoring and oversight of 81 banks statewide. Other agencies that typically participate in the regulation and approval of conservation banks include the U.S. Army Corps of Engineers (USACE), U.S. Environmental Protection Agency (USEPA), Natural Resources Conservation Service (NRCS), U.S. Fish and Wildlife Service (USFWS) and the National Oceanic and Atmospheric Administration National Marine Fisheries Service (NOAA NMFS).

To read more about one of these successful partnerships, please visit USFWS’ newsroom.

Learn more about CDFW’s Conservation and Mitigation Banking program, on our website.

All photos courtesy of U.S. Fish and Wildlife Service.

Top photo: A herd of cattle graze atop a hillside at Sparling Ranch near Hollister, Calif. Photo by Ashley Spratt/USFWS.

CDFW Scientific Aide Aimee Taylor prepares electrofisher to harmlessly catch Paiute cutthroat trout in North Fork Cottonwood Creek.


The extremely rare Paiute cutthroat trout (PCT). Photo by William Somer for CDFW.


Aimee Taylor and Senior Environmental Scientist Jeff Weaver electrofish PCT in North Fork Cottonwood Creek.


Jeff Weaver, USFWS Biologist Chad Mellison and others take genetic samples from the fish.


The project’s lead biologist, Bill Somer, and Chad Mellison transfer the trout from CDFW’s tank truck to cans for the ride to Silver King Creek, by pack mule.


The CDFW-FWS-USFS team packs pure PCT in milk cans through the Silver King drainage.


Bill Somer releases Paiute cutthroat trout into Silver King Creek, above Llewellyn Falls.


Team members measured each Paiute cutthroat trout caught at White Mountain.

The California Department of Fish and Wildlife (CDFW), U.S. Fish and Wildlife Service (FWS), and U.S. Forest Service (USFS) have returned a rare trout species to its home water after a 71-year absence.

In 1946, poachers were decimating the Paiute Cutthroat Trout (PCT), a species whose native range was limited to a nine-mile section of Silver King Creek (Alpine County). To ensure the species’ survival, the USFS and Eastern Packers Association translocated 401 of these fish to North Fork Cottonwood Creek in Inyo County’s White Mountains. This population has persisted in isolation from other forms of trout and has recently provided important restoration options for resource managers. None of this would have been possible without the foresight of concerned biologists seven decades ago.

The conservation history of this rare trout is complex. The initial “conservation” measure was entirely inadvertent. In the early 1900s, Basque sheepherders in the area caught and transported PCT into the previously fishless portion of Silver King Creek above Llewellyn Falls. This early within-basin transfer was the salvation of the PCT, since non-native species were later introduced below the falls. The falls prevented non-natives from reaching the habitat above and protected PCT from hybridization and competition.

The FWS listed PCT as endangered under the Endangered Species Preservation Act of 1966 – the precursor to the federal Endangered Species Act (1973). The species was down-listed to threatened status in 1975, in order to facilitate management and restoration and to allow regulated angling. In 1994, CDFW, FWS and USFS began developing a restoration plan to remove non-native fishes from Silver King Creek and return the PCT to its native waters. From 2013 to 2015, the partner agencies treated 11 stream miles of Silver King Creek and three tributaries below Llewellyn Falls with a fish toxicant, rotenone, to remove all non-native fish species.

The PCT population in Upper Fish Valley, an area of Silver King Creek above the falls, has been considered a primary source for restocking the recovery area. Unfortunately, that population was heavily impacted by the extreme 2012-2016 drought. During this extended drought, lack of snow cover resulted in the stream freezing almost solid during cold snaps. In order to offset the resulting population decline, the partner agencies caught 86 pure PCT in North Fork Cottonwood Creek. On August 23, 2017, the fish were planted back into Silver King Creek above Llewellyn Falls.

Agency staff met in the White Mountain Wilderness (Inyo National Forest) and, along with volunteers and pack mules, hiked from their campsite to North Fork Cottonwood Creek. There, the team used electrofishers to retrieve descendants of the fish moved back in 1946. The fish were hauled out by mule, put in a specialized transport truck, and driven approximately 100 miles to the Carson Iceberg Wilderness. Another mule team then hauled them back to Silver King Creek. Thanks to careful handling by the collection and transport teams, every fish survived the trip home.

Due to its limited habitat, the Paiute Cutthroat Trout has been called the rarest, but most recoverable, form of trout in the United States. With the most recent success of this partnership, and due in large part to the foresight of conservationists in the past, the future looks bright for this beautiful native salmonid.

Learn more on the Paiute cutthroat trout web page.

Photos by Joe Barker, courtesy of U.S. Fish and Wildlife Service, except as noted.

Top photo:
Liz Vandentoorn, from the Inyo National Forest Region 5 Center of Excellence, leads a pack mule team and state and federal scientists to North Fork Cottonwood Creek to capture Paiute cutthroat trout and return them to Silver King Creek.