Science Spotlight

Environmental Scientist Laura Cockrell records the weight of a wild turkey at Little Dry Creek prior to banding.


Wild turkeys banded in 2019 and 2020 are given one traditional, butt-end band on one leg and one rivet band on the other.


Environmental Scientist Laura Cockrell shows off the supply of butt-end bands prior to banding.

Turkey hunters in parts of Butte and Glenn counties who are skilled and lucky enough to bag a tom this spring may be in for a pleasant surprise: Their bird may be sporting some jewelry – a band on each leg.

Since early February, CDFW biologists at the Upper Butte Basin Wildlife Area – supported by the National Wild Turkey Federation (NWTF) – have been busy trapping and double-banding wild turkeys at the wildlife area’s Howard Slough and Little Dry Creek units. So far this year, some 45 turkeys have been banded, which include toms, hens and young males known as “jakes.”

The staff and volunteers have just about a month and a half to trap and band all the wild turkeys they can between the close of the waterfowl hunting season and the start of the spring wild turkey season in mid-March. It’s part of an innovative research effort aimed at better understanding the characteristics, growth rates, habitat use, range and abundance of the growing population of wild turkeys using the wildlife area.

Bird bands long have been an important research tool for biologists and considered a prize among many hunters who are allowed to keep them after reporting the band information. The Upper Butte Basin turkey banding project is the only one of its kind in the state, making those turkey bands a rare commodity and a valuable potential data source.

In addition to the banding, the turkeys are weighed, sexed and measured at various points before being released.

The wild turkey study began at the wildlife area in 2015 along with the launch of limited spring wild turkey hunts there. NWTF helped secure grant funding to start the hunt program and initiate the research effort. The funds came from the sale of upland game bird hunting validations and stamps required of upland game bird hunters.

“We thought it would be great to start getting an abundance estimate for the turkeys that we do have out here to make sure that we weren’t harming the population through the hunt program and also to see how much hunter opportunity we could potentially utilize,” said Kevin Vella, NWTF’s district biologist for California, Nevada, Oregon and Washington.

The spring wild turkey hunt program has been so successful and popular over its short history funding for the program and its research component will continue under CDFW’s general budget moving forward.

“I think Howard Slough especially offers some of the best turkey hunting I’ve seen anywhere,” said Upper Butte Basin Wildlife Area Manager Tim Hermansen. “Certainly, youth hunters have an excellent opportunity out here.”

Spring turkey hunts at both the Howard Slough and Little Dry Creek units are limited to lottery drawings through CDFW’s website in order to ensure an uncrowded, high-quality hunting experience. The hunter quota and the turkey harvest both have grown over the years along with the local turkey population. Hunter success ranged from 30 to 60 percent during the 2019 spring season but reached 100 percent for the youth hunt at Howard Slough in 2018.

Back to those double-banded birds.

Although 101 turkeys were banded at the wildlife area between 2015 and 2019, only three banded turkeys have been reported by hunters. That leads biologists to believe most of the turkeys have been prying off the traditional, “butt-end” bird bands, which have two edges that butt evenly together when clamped on.

The NWTF has since supplied Upper Butte Basin with rivet bands that are made of a harder metal and riveted closed when attached. The turkeys banded in 2019 and 2020 now receive a butt-end bird band on one leg and a rivet band on the other. Any of those harvested birds wearing a single rivet band will confirm suspicions that the birds have been prying off the butt-end bands.

“That’s the downside of doing any kind of novel research,” explained Laura Cockrell, a CDFW environmental scientist based at the Upper Butte Basin. “You only have your own mistakes to learn from.”

CDFW Photos. Top Photo: Upper Butte Basin Wildlife Area Manager Tim Hermansen releases a wild turkey after banding as Fish and Wildlife Technician Derek Schiewek and Seasonal Aid John Davis look on.

Media Contact:
Peter Tira, CDFW Communications, (916) 322-8908

Logan Weyand, left, a veterinary student form Washington State University, and Drew Trausch, a scientific aid with CDFW’s Big Game Program, help capture and collar a cow Roosevelt elk in Humboldt County this past fall. CDFW photo by Shwn Fresz.


CDFW crews work quickly to tag and collar a tranquilized cow elk in Humboldt County. CDFW photo by George Harse.


Sporting ear tags and a GPS tracking collar, a cow Roosevelt elk returns to heavy timber after being sedated. CDFW photo by Andrew Trausch.


Ear tags provide biologists with visual identification of Roosevelt elk study animals while GPS tracking collars can provide years worth of detailed date on movement and habitat preferences. CDFW photo by George Harse.

State biologists are now learning a great deal about California’s largest land mammal.

Roosevelt elk are one of three subspecies of elk native to California, joining the tule elk (the smallest of the three) and the Rocky Mountain elk. While a bull Rocky Mountain elk will have larger and more impressive antlers, the Roosevelt elk bests it in body mass. A bull Rocky Mountain elk can reach 700 pounds while a bull Roosevelt can exceed 1,000 pounds.

Despite their massive size and majestic appearance, Roosevelt elk have proved an elusive research subject because of the dense forests they inhabit. Aerial surveying and trapping – standard tools for counting and collaring deer, elk and bighorn sheep in more open parts of the state – can be challenging for Roosevelt elk moving in and out of heavy coastal timber.

While deer often can be darted and tranquilized using a biologist’s truck as cover, Roosevelt elk are more wary and vehicle-shy, often requiring a lengthy stalk and serious hunting skills to get within the 50-yard effective range of a dart gun. In some cases, it can take more than 100 hours to capture and collar an individual Roosevelt elk.

In an attempt to close the knowledge gap, CDFW recently initiated one of the largest Roosevelt elk capture and collaring efforts in state history, targeting a population of Roosevelt elk living along the U.S. 101 corridor in Humboldt and Del Norte counties. The effort is part of an ongoing study that began in 2016, explained Carrington Hilson, CDFW’s lead elk research biologist on the north coast. The study will continue through 2025.

Since November, Hilson and her colleagues have affixed GPS tracking collars on 24 cow Roosevelt elk in Humboldt and Del Norte counties to monitor their movements and migrations. CDFW biologists plan to collar another 14 cows this winter.

Several ancillary projects – estimating populations using fecal DNA, looking at calf survival and understanding habitat use – are also underway at Humboldt State University in Arcata in coordination with CDFW that will add to the state’s body of knowledge.

A few factors are driving the research interest, explained Kristin Denryter, the Sacramento-based senior environmental scientist who oversees CDFW’s Elk and Pronghorn Antelope Program. The first is an increasing number of human-elk conflicts along the U.S. 101 corridor that include vehicle collisions, property damage and agricultural losses suffered by north coast farmers and ranchers.

The second driver is technology. Advances in GPS tracking collars make them an increasingly valuable research tool. The new elk collars will record data every six hours over the life of the study and deliver that information daily to CDFW biologists.

Lastly, there is the California Essential Habitat Connectivity Project and U.S. Department of the Interior Secretarial Order 3362 (SO 3362).

Signed in 2018, SO 3362 directs federal agencies to work with California and other western state wildlife agencies to improve the quality of big-game winter range habitat and migration corridors on federal land. The order provided funding for CDFW to acquire the 38 GPS tracking collars and accelerate its research efforts. The collar data will improve understanding of movement and habitat use to inform habitat enhancement on public lands as well as help guide development of potential crossing structures to not only improve habitat connectivity but to also improve public safety by reducing vehicle collisions. CDFW has partnered with CalTrans on improving connectivity as part of the California Essential Habitat Connectivity Project.

A Roosevelt elk stakeholder group made up of CDFW representatives, tribal interests, farmers, ranchers and local officials is also being developed.

Official estimates put the Roosevelt elk population along the U.S. 101 corridor in Humboldt and Del Norte counties at 1,600 animals. Biologists, however, suspect those estimates to be low. In an attempt to reduce growing human-elk conflicts, CDFW issued 20 additional Roosevelt elk tags during the 2019 hunting season through its SHARE program, which provides public hunting opportunities on private land through cooperating landowners. CDFW is currently petitioning the California Fish and Game Commission to increase the allotment of Roosevelt elk tags available along the north coast in the 2020 fall hunting season.

Translocations, limited hunting, high calf survival, and conservation management have all helped boost Roosevelt elk populations from lows in the early 1900s to a robust statewide estimate today of 5,700 animals. Roosevelt elk also occupy parts of Mendocino, Trinity, Shasta, Tehama and Siskiyou counites.

The U.S. 101 corridor population in Humboldt and Del Norte counties has proved particularly adaptable – as comfortable roaming the beaches of state parks as they are grazing in open alfalfa fields or wandering underneath the forest canopy. That’s made them especially popular with tourists and some locals but not so much with farmers and ranchers suffering property damage and crop losses from the expanding herds.

Locations of bird surveys throughout Northern California in a region representing more than 40 percent of all California’s coniferous forests. CDFW has been monitoring wildlife at these locations since 2002 to help inform conservation efforts. Photo courtesy of Dr. Brett Furnas.


An automated sound recorder used to survey songbirds. These devices were programmed to make three 5-minute recordings before, at, and after sunrise –repeated over three consecutive mornings. The timing of the recordings is significant because different species tend to sing at different times in the morning. Photo courtesy of Dr. Brett Furnas.

New research shows climate change may harm migratory songbirds. Saving their forest habitat may help.

Songbirds that travel to northern California each summer from winter ranges in Central and South America appear to be more sensitive to climate change than other types of songbirds, according to new research by CDFW Wildlife Ecologist Dr. Brett Furnas.

In a new paper published in the journal Biological Conservation, Dr. Furnas analyzes 14 years of data taken from the surveys of songbirds living in northern California conifer forests. The bird surveys were done in the Klamath Mountains, Southern Cascades and North Coast Ranges, a region representing 42 percent of all conifer forests in the state.

“The data is especially significant because it is representative of such a large region,” said Dr. Furnas.

Research was completed using automated sound recorders which captured the calls of songbirds at over 1,000 sites between 2002 and 2016. Birds were surveyed at their annual summer breeding grounds about a month after arriving from their winter homes.

Dr. Furnas studied three types of songbirds: year-round residents; short-distance, altitudinal migrants which winter at lower elevations and breed at higher-elevations; and long-distance, Neotropical migrants that winter in Mexico, Central America and South America and breed in California.

“The research alone is an amazing part of this story. Each of the 1,000-plus survey sites required someone to drive to the middle of the forest, hike for an hour or more and install survey equipment,” said Dr. Furnas.

The data shows that Neotropical migrant songbirds are shifting their summer ranges to higher elevations where the climate is cooler. But there’s a downside to the new migration pattern: The long journey reduces the Neotropicals’ flexibility when it comes to breeding behavior. Adjusting to changes in temperature and available food resources in California ultimately hurts their reproductive success.

“Neotropicals’ sensitivity to climate change makes them a conservation risk. It’s unclear if they can adapt as climate continues to warm,” said Dr. Furnas.

There was less evidence of elevational shifting for resident and altitudinal songbirds, indicating they might not be as vulnerable to increases in temperature. This is likely because species that migrate shorter distances – or don’t migrate at all – have more time to prepare for the breeding season. They also have more time to establish a territory, sing to attract a mate and gather food to help raise a brood.

The Neotropicals’ vulnerability is exacerbated by other factors as well. One consequence of the compressed breeding cycle is that the birds can’t afford to tone down singing on hot days when it becomes metabolically taxing. In contrast, resident birds tend to sing less on hot days.

Dr. Furnas sees conservation of mid-elevation conifer forests as part of the solution. Neotropicals are expanding their range to about 5,000 feet and above.

“Middle-elevation conifer forests appear to have features of natural climate refugia. Conserving these forests is crucial,” he said.

However, the natural climate refugia identified by Dr. Furnas have their own vulnerabilities. “If you think of mountains like a triangle, there’s less land area in the middle-elevation forests that Neotropicals are shifting to than in the lower elevation forests they’re abandoning. The availability of forest habitats at higher elevations could be limited in the future due to faster rates of warming at those elevations,” Dr. Furnas said.

For these reasons, the middle zone is a sweet spot for birds. “An increasing number of birds will be crowding into this sanctuary,” he said.

Dr. Furnas’ ultimate message is that research with an emphasis on biodiversity monitoring will be essential to future conservation efforts. Research based on biodiversity monitoring can help identify species and habitats that are most in need of conservation. It can also help conservationists and policy makers assess the effectiveness of conservation actions.

Read Dr. Furnas’ paper: Rapid and Varied Responses of Songbirds of Climate Change in California Coniferous Forests

CDFW Photos. Top Photo: Long-distance Neotropical migrants like the Hermit Thrush may be more vulnerable to climate change than other types of songbirds.

Media Contact:
Ken Paglia, CDFW Communications, (916) 322-8958

Forensic Specialists Kelly Carrothers (l) and Ashley Spicer, from the California Department of Fish and Wildlife, remove samples from tusk at the La Brea Tar Pits, in Los Angeles.  

In Southern California, there are two facilities that offer fascinating looks at the types of animals that roamed the land millions of years ago. The Western Science Center in Riverside County is home to 100,000 fossils and artifacts, all unearthed during construction of a nearby reservoir. The La Brea Tar Pits in neighboring Los Angeles County serves a similar purpose, storing a staggering 35 million prehistoric specimens discovered in and around the natural pits that continue to seep asphalt in the area.

Both facilities gladly open their doors to tourists and school field trips. Recently, they also welcomed two California Department of Fish and Wildlife forensic scientists, who traveled from Sacramento to collect samples of ivory tusks taken from Mammoths and Mastodons for a very specific purpose. Ashley Spicer and Kelly Carrothers came to collect the samples to take back to CDFW’s Wildlife Forensics Lab in Sacramento. The lab itself serves a number of purposes. In this case, the staff are collecting ivory samples for DNA testing and identification, under the auspices of a state law (AB 96) that makes it illegal to trade ivory or rhinoceros horn.

The Wildlife Forensics Lab maintains a species database that helps identify the origin of all kinds of ivory samples. The ability to pinpoint the source of any given ivory sample is critical when it comes to prosecuting criminal cases brought against suspected ivory traffickers.

“Mammoth and mastodon are species that are protected under AB 96 – you cannot commercialize them,” explained Spicer. “Examining the DNA allows us to identify the species of origin for any ivory-bearing species -- mammoth, whale, walrus, warthog or hippo. So, we can first distinguish whether a sample is ivory or not ivory, and whether it’s a fake or synthetic. If it is genuine ivory, then we can test it to see what was the species of origin.”

A key element of AB 96 was the closing of a loophole in previous laws. That loophole allowed the continued sale of tusk from mammoths and mastodons, because those animals were extinct. The exemption gave traffickers the chance to fraudulently claim that they were trafficking in legal material. Now that all forms of ivory trafficking are illegal – regardless of whether the species of origin is extinct – CDFW officials hope that an expanded DNA database will be the key to shutting down the ivory trafficking trade in California.

“The laboratory capability we have today helps us differentiate between ivory taken from an elephant that was poached in Africa within the last few years vs. ivory that was from an extinct species like a mammoth or a mastodon,” said Captain Patrick Foy of CDFW’s Law Enforcement Division. “This is huge for us – (now) we can actually prosecute these cases and convict these criminal poachers, to make the cases we couldn’t make 10 years ago,” said Foy.

CDFW is particularly grateful for the opportunity to obtain samples from the two Southern California facilities noted for their extensive fossil collections. “To be able to work with them (Western Science Center and La Brea Tar Pits) is a really exciting collaboration,” said Spicer. “These samples will be used for forensic testing methods, and ultimately for forensics case work that will help preserve some of our most precious natural resources.”

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CDFW Photos. Forensic Specialists Kelly Carrothers (l) and Ashley Spicer, from the California Department of Fish and Wildlife, examine tusk at the Western Science Center in Riverside County.

A healthy steelhead trout surveyed at Pescadero Creek Lagoon Complex in 2017


The aftermath of a winter sandbar breach 2014. These nearly annual breaches resulted in large die-offs for the lagoon’s steelhead.


A manual breach of Pescadero Creek Lagoon Complex. Managed breaches of the lagoon can prevent fish kills caused by turbulent natural breaches. Photo Courtesy of UC Davis School of Veterinary Medicine

There’s a dichotomy in the way Pescadero Creek Lagoon Complex in coastal San Mateo County has both supported—and been detrimental to—steelhead trout for much of the past 25 years.

On one hand, the lagoon complex—the largest tidal marsh between Elkhorn Slough and the San Francisco Bay estuary—boasts high growth rates for Central California Coast Steelhead. The lagoon system allows the species, which is federally listed as endangered, to reach a size that increases their likelihood of surviving at sea. Steelhead also use the system for juvenile rearing and resting during migration.

On the other hand, nearly every year since the mid-1990s, the lagoon faced harsh fall/winter sandbar breaches that filled the system with oxygen-depleted water and spread toxic sediment produced by the breakdown of organic matter like plant material in the absence of oxygen.

These breaches often resulted in large die-offs for the lagoon’s steelhead population. Historically, population estimates have reached as many as 17,000 steelhead rearing into the fall.

“It was a one-two punch where fish faced lack of oxygen and got hit with harsh toxic compounds. It was really unfortunate because the lagoon system works so well to grow steelhead, but we were losing the production every year,” said District Fisheries Biologist Jon Jankovitz.

Efforts to actively manage breaches began in 2012, but were stalled in 2014 and 2015 when the steelhead population was diminished due to drought conditions. In 2015, the California Department of Fish and Wildlife (CDFW) and the National Oceanic Atmospheric Administration (NOAA) partnered with the Department of Parks and Recreation (DPR), which owns much of the land associated with the complex, in adopting a monitoring and management plan.

In 2016, a significant fish kill caused by a turbulent sandbar breach prompted further action. CDFW, NOAA and DPR resumed active management to improve water conditions and prevent the deadly breaches.

The restoration team installed a sandbar dam at a major channel to slow the release of oxygen-depleted water and sediment into the system. Staff also preemptively manually breached the lagoon mouth on occasions when they anticipated a harmful natural breach.

Jankovitz conducts weekly water quality monitoring and twice-monthly dry-season fish sampling to inform management decisions. He produces an annual report on the health of the steelhead population and a summary of seasonal water quality transitions.

So how has active management faired? There hasn’t been a significant fish kill since 2016.

“We’ve saved the steelhead population for the last couple of years. We’re fortunate for the success we’ve had so far,” said Jankovitz.

Another mark of success has been the documented presence this year of sexually mature holdovers, meaning steelhead that were reared in the lagoon for two seasons even though they were large enough to smolt (i.e. migrate to sea).

“This obviously couldn’t happen if there was a fish kill the year prior. These holdovers represent a life history strategy that may fill in gaps during down reproductive years or periods of poor ocean conditions,” said Jankovitz.

There’s a long-term restoration plan in the works which would likely involve structural changes, such as relocating culverts and breaching levees, to alter the dynamics of how much tide flows in and out of the system. The plan includes a sediment removal project that was implemented in 2019 to increase fish passage.

Ultimately, CDFW and DPR would like to keep the system thriving without active management. “We don’t love breaching the lagoon manually because it can be stressful for fish and other aquatic species,” Jankovitz said.

Meanwhile, fostering an environment in Pescadero Creek Lagoon Complex that supports a large population of fast-growing steelhead continues to be top priority.

“Aside from being a native California species with a long history of recreational and angler use, steelhead are a great biological indicator of the health of streams and lagoon systems. The ecology of these systems would likely fall apart without them,” Jankovitz said.

Photos courtesy of CDFW District Fisheries Biologist Jon Jankovitz and the Bodega Marine Lab at University of California, Davis. Top Photo: District Fisheries Biologist Jon Jankovitz with a healthy Pescadero juvenile steelhead.

Media Contact:
Ken Paglia, CDFW Communications, (916) 322-8958