Our research projects are always evolving as research advances and ecological information needs and critical threats shift over time. We are always writing proposals for new research projects. Our current work extends across California and the Southwest, and into Central America, and we work on a wide range of taxa and in varying habitats.
Despite this wide range of research experience, there are several species, habitats and topics that we view as critically important to avian research and conservation. We have worked in these research areas for many years, over many projects, establishing ourselves as experts in these fields. These long-term research areas are outlined below.
Better Understanding Species of Conservation Concern
We conduct work on all parts of the life cycle for several threatened and endangered species. We have done extensive research for many years on the breeding biology and population dynamics of both Yellow-billed Cuckoos and Southwestern Willow Flycatchers in mutliple locations including the Kern River Valley, CA, the Owen’s River Valley, CA, Southeastern Arizona, and the Vanderberg Air Force Base. We rencently concluded 14 years of research and monitoring of Yellow-billed Cuckoos on the Palo Verde Ecological Reserve (PVER) for the Bureau of Reclamation. In 2022, in collaboration with multiple partners, SSRS organized and led a Rangewide Survey of Yellow-billed Cuckoos across eleven western states for a Competitive State Wildlife Grant (CSWG).
The Southern Sierra Research Station, under the leadership of Mary Whitfield, has worked on several projects examining the wintering distribution and ecology of Willow Flycatchers, with more work upcoming. Information about migratory avian species on their wintering grounds often lags behind research on the breeding grounds, but can be critically important to understanding their declines. We are working on more ways to collaborate with local scienctists and social scientists in Central America to help fill these critical research gaps. We have also collaborated on projects linking breeding and wintering birds, such as the Bird Genoscape Project.
Additionally, we have done extensive work on Pinyon Jays and other Pinyon Juniper woodland-dependent species, based out of our satellite office in New Mexico. Pinyon Juniper woodlands are a critical habitat for many avian Species of Greatest Concervation Need (SGCN), such as the Black-throated Gray Warbler and Juniper Titmouse, but is threatened by climate change, drought, fire regimes, insect infestations and other changes. Another species of interest in Northern New Mexico that our staff has expertise in is the Brown-capped Rosy Finch. We hope to expand our work on this species in future years.
The Southern Sierra Research Station has also worked extensively on the Tricolored Blackbird. We are have conducted Tricolored Blackbird habitat preference studies here in the Kern River Valley to create, protect, and enhance habitat in our area, partnering with Audubon, USFWS and others. Currently we are pursuing new research to utilize our greatly expanded Motus Wildlife Tracking infrastructure and finer scale Node networks to understand the movement ecology of Tricolored Blackbirds, particularly in the breeding season.
We have also assisted in the ongoing efforts to evaluate the populations of the threatened Inyo California Towhees, including on the China Lake Naval Air Weapons Station (see map in link), as well as conducted research on LeConte’s Thrasher.
Although much of our expertise and research has been conducted on avian species, we also have a great interest and experience with research on non-avian species of concern in our area such as the Alkali Mariposa Lily , Foothill Yellow-legged Frogs, Pond Turtles, Blunt-nosed Leapoard Lizards, Monarch Butterflies, and Southern Foxtail Pines. We have experts in Entomology and Herpetology on our staff, and do collaborative work with a local Bat Biologist.
Understanding the use of Critical Habitats
Many of the species that our station biologists have researched for many years are dependent on southwestern riparian habitats. Riparian habitats and desert springs are critical areas of productivity in an otherwise mostly arid landscape. These habitats are essential during both the breeding and migration seasons for many of the species we study. They have also been drastically altered over the past 100 years by dams and flood control, agriculture and increasing societal water demands. We continue to examine the importance and roles of these habitats throughout the southwest, as well as evaluate the effectiveness of restoration efforts. We are building and utilizing Motus tracking and ARU (autonomous recording unit) technology to increase our understanding of these habitats and how they are used by various fauna.
Habitat Assessments and Species Surveys
Another component of the work we do is conducting species surveys and habitat assessments for organizations to help them evaluate habitat, land aquisitions, or restoration projects. We have conducted surveys on a wide range of plant and animal species in many different habitat types. This work is often for the purpose of creating management plans for the land in question and the species that inhabit it. Recent work includes multi-species surveys for The Nature Concervancy on the newly aquired Frank and Joan Randall Preserve , Alkali Mariposa Lily and Blackbird Surveys on the Kern River Valley Heritage Foundation properties in Lake Isabella, CA, Bioblitz all-species survey on the Quarter Circle 5 Ranch Property, Cowbird and Avian Monitoring at Anza Borrego State Park, Avian monitoring at Naval Weapons Air Station, China Lake, CA, and Avian Monitoring on the Tejon Ranch, CA.
MAPS Bird Banding Station
Since 1998, SSRS has operated a MAPS bird banding station from May to August on Audubon California’s Kern River Preserve. The MAPS (Monitoring Avian Productivity and Survivorship) program is a continent-wide collaborative effort organized by the Institute for Bird Populations (https://www.birdpop.org/pages/maps.php) to assist the conservation of birds and their habitats through bird banding research. MAPS data is publicly accessible (MAPS Data Exploration Tool) and is currently being used to estimate demographic rates, such as productivity (young produced per year) and the annual survival of young and adult birds. These parameters are then used to identify which parts of the annual cycle limit population growth or drive population declines. Since 1989, more than 1,200 MAPS stations spread across nearly every state and Canadian province have collected more than 2.5 million bird capture records.
In addition to the valuable banding data collected at our station, we also collect feathers from birds that visit our nets and send hundreds of feather samples to the Bird Genoscape Project (birdgenoscape.org) each year. The Bird Genoscape Project then extracts genetic information from the tips of feathers to link genetically distinct populations between their breeding grounds, migratory routes and wintering grounds.
Our MAPS station is currently completely self-funded, which means we rely on donations to keep it running. We are currently in great need of funding for our 2024 season. Because we already have equipment and infrastructure, we can run an entire MAPS season for only $8,000!
Please consider giving a donation to help us keep our banding station open. Long term studies like this one are some of the most ecologically critical, but also the hardest to continue funding. Every dollar helps! And if you are interested in visiting our banding station and seeing what we do, please contact us!
Motus Wildlife Tracking Systems
The Motus Wildlife Tracking System is a collaborative network of over 1,600 automated radio-telemetry receiving stations located across North and South America. SSRS has played a critical role in the growth of the Motus network across the west. Led by Research Director, Mary Whitfield, and Senior Biologist, Pat Lorch, SSRS is actively involved in both the planning and the building of Motus stations all over California. Read more about Motus and SSRS’s continued work in deploying and utilizing this technology across the west.
Breeding Biology and Population Dynamics of Yellow-billed Cuckoos
The Yellow-billed Cuckoo (Coccyzus americanus) is a neotropical migrant that historically bred in riparian habitats throughout much of North America. Since the late 1800s many of the riverside forests that cuckoos depended upon, particularly in the West, have been destroyed or degraded by human activity. As a result, both the range and numbers of breeding cuckoos have decreased dramatically and the western distinct population segment of the Yellow-billed Cuckoo was listed as a Federally Threatened Species in 2014.
Our research focuses on conservation of the cuckoo, investigating its breeding ecology, developing new monitoring techniques, identifying limiting factors, and developing management recommendations.
Photo by Sasha Robinson
We hope to expand our research in the near future to look more closely at movements using Motus and research into diet and prey availability. In partnership with many other organizations and agencies, we recently completed a range-wide survey of Yellow-billed Cuckoos in the western United States.
We conduct most of our research in the Kern Valley in CA and other riparian areas in the west (e.g. the Lower Colorado River and the San Pedro River). We have been monitoring the Kern River Valley cuckoo population for over 20 years. The Kern River Valley has one of the few remaining western Yellow-billed Cuckoo populations in California and has been a consistent cuckoo breeding area for over 40 years. Additionally, the Kern River Valley contains one of the largest remaining contiguous cottonwood/willow forests in the state of California which provides critically important habitat for the western Yellow-billed Cuckoos.
Southwestern Willow Flycatchers – Breeding Biology and Population Dynamics
The southwestern subspecies of the Willow Flycatcher (Empidonax traillii extimus) is rare throughout most of its breeding range. It was once a common breeder in riparian habitats of southern California, southern Nevada, southern Utah, Arizona, New Mexico, western Texas, and extreme northwestern Mexico. Due to its low numbers and limited distribution, the U.S. Fish and Wildlife Service (USFWS) listed the Southwestern Willow Flycatcher as endangered in 1995. In 1989, we initiated a long-term study to investigate factors that affect the numbers and reproductive success of Southwestern Willow Flycatchers in the South Fork Kern River Valley (SFKRV). Since then, we have performed surveys for breeding birds and monitored their reproductive success through intensive field efforts. We have also directed considerable attention on the effects of Brown-headed Cowbird parasitism because it can negatively affect their nesting success. Cowbird control efforts have reduced the size of the Brown-headed Cowbird population over the course of the study and effectively reduced parasitism rates. Despite this reduction, the population of Southwestern Willow Flycatchers has not increased in response to the release of parasitism pressure. Factors other than Brown-headed Cowbird parasitism likely play an important role in regulating numbers of Southwestern Willow Flycatchers in the study area. However, these efforts may have also contributed to Least Bell’s Vireos (Vireo bellii pusillus) returning as a nesting species in the area in 2014 (they have not been documented nesting here since the early 1900s). We are currently investigating the roles that habitat quality, food abundance, climate, and geographic isolation play in limiting population growth for the flycatcher. We also collaborate with other organizations to monitor these birds in other regions such as the Owens Valley, CA, Santa Ynez River, CA and southeastern Arizona.
Photo by Bob Steele
Willow Flycatcher – Wintering Distribution and Ecology
The Willow Flycatchers (Empidonx traillii) were listed as endangered in California by the California Department of Fish and Wildlife Service in 1990. Breeding requirements, habitat, and threats to the species have been studied extensively for nearly three decades throughout the west and are fairly well understood. However, relatively little work has been done to fully understand the status, habitat, and threats to this species on its wintering grounds, where it spends the majority of its life, and where habitats are less stable and under greater threat. Ecologists have long recognized that conservation measures on the breeding grounds of neotropical migrant songbirds may not succeed if wintering ecology is not understood and winter habitat is not protected. It seems likely that availability of quality winter habitat in Latin America will become a major concern for willow flycatchers (and other North American migrants) in the near future because of continuing forest destruction, increasingly intensive agricultural practices, and other land conversions. Approximately 90% of the Willow Flycatcher wintering sites we have visited in Latin America are not legally protected from development or destruction.
For twenty years, we have conducted wintering Willow Flycatcher research in Latin America. Although the four subspecies of Empidonax traillii have well-defined geographical distributions on their breeding grounds, the same segregation does not hold true in wintering areas. Our previous work has focused on wintering sites in Costa Rica, Ecuador, El Salvador, Guatemala, Nicaragua, Panama and Mexico, and accomplishments to date include:
- Locating and mapping wintering sites in seven countries;
- Description of the primary components of wintering habitat;
- Capture and banding of more than 400 willow flycatchers;
- Establishing study sites in Nicaragua.
- Recapture of willow flycatchers banded in the U.S.;
- Collection of blood & feather samples for genetic analysis;
- Collaborating with the Bird Genoscape Project (https://www.birdgenoscape.org/) to link breeding Willow Flycatcher populations with wintering sites.
- Collaborating with Paso Pacifico (https://pasopacifico.org/) for work in Nicaragua and El Salvador.
- Collaborations with Latin American scientists for effective conservation planning.
From this research, we have gained a better understanding of site fidelity, the fact that two or more subspecies can winter at the same sites, characteristics of winter habitat, current habitat condition and changes over time. In addition, we are starting to better understand the threats facing these birds on their wintering grounds. We are planning to continue our work on wintering willow flycatchers, one of our main goals is to expand our long-term winter ecology research into Costa Rica.
This research on ecology of wintering Willow Flycatchers is something we hope to expand and grow in future years. However, international funding is particularly difficult to secure. If you are interested in collaborating or know about potential funding for this type of work, please reach out!
Tricolored Blackbirds
Tricolored Blackbirds were once one of the most abundant birds in California. In the 1930s, conservative estimates indicated that the statewide population was between 2 and 3 million birds. Since that time statewide populations have steeply declined. The most recent triennial statewide survey (2022) estimated a statewide population of 218,000 birds.
While that population is up by 41,000 birds from the last estimate, it represents just 55% of the estimated population in 2008. Reasons for this decline, current and historical, are primarily attributed to habitat loss. Although this species has adjusted to nest in cropland across much of California, agricultural nesting sites may create population sinks if grain fields are harvested while young are still in the nest. The destruction of one colony can mean the reproductive failure of thousands of birds.
The Kern River Valley hosts a Tricolored Blackbird population that is not dependent on the use of agricultural fields for foraging and nesting. Here Tricolored Blackbirds nest in both native (stinging nettle, sandbar willow, cattail, mulefat) and non-native (Himalayan blackberry) substrates. They forage and breed in wetlands, riparian habitat, irrigated pastures and upland shrublands. Keeping these areas wet and suitable during drought years is a critical need in our area. Recent studies have shown a high degree of gene flow across breeding populations, suggesting that conservation in successful breeding areas remains important for the entire species.
SSRS has focused efforts on understanding Tricolored Blackbird habitat preferences in the Kern River Valley. We have used this information to inform management and more specifically to create, protect, and enhance habitat in our area, partnering with Audubon, USFWS and others to increase our impact in past projects. Another main focus of our research is to understand the movement ecology of Tricolored Blackbirds, particularly in the breeding season. To do so, SSRS has utilized the Motus Wildlife Tracking Network and greatly expanded infrastructure (through many different projects) throughout the range of Tricolored Blackbirds. SSRS is now poised to answer many important questions pertaining to Tricolored Blackbird movement within and between breeding seasons.
We will continue to survey for Tricolored Blackbirds by participating in the triennial statewide surveys in mid-April. If you are interested in participating in these surveys you can find information at the tricolored blackbird portal website.
