Once considered common throughout much of the Sierra Nevada, the Willow Flycatcher (Empidonax trailii) has declined precipitously since the middle of the twentieth century. By the late 1990s the region’s population was estimated at just 300-400 individuals. Willow Flycatchers appear to have stopped breeding at many historically occupied meadows south of Lake Tahoe and 6% annual declines in population size are reported for the area between the south fork of the Feather River and Lake Tahoe. Recent studies suggest one explanation of the decline is poor nesting success, largely due to meadow desiccation, which allows mammalian predators easier access to Willow Flycatcher nests.
Causes of meadow desiccation throughout the Sierra Nevada include streambank erosion due to livestock grazing and road construction, water diversions, climate change, and other factors. Yet, many of these factors would appear to play little if any role within the confines of Yosemite National Park, where IBP research has documented that the species has stopped breeding in recent decades.
IBP’s work on Willow Flycatcher in the Sierra Nevada is focused on understanding causes of the population decline, assessing the current status of the species throughout the region, and identifying and facilitating opportunities for restoration and conservation.
For more information about IBP’s work with Willow Flycatchers, please contact Helen Loffland.
With funding from the National Fish and Wildlife Foundation, IBP recently led a partnership to collate recent Willow Flycatcher survey results from state and federal agencies and other groups across the Sierra Nevada and southern Cascades of California, and develop an updated range map and population estimate for Willow Flycatcher across the region. The results, which we expect to publish in a peer-reviewed paper shortly, document alarming declines and near-extirpation of the species in the region south of Lake Tahoe.
The updated information we produced about the current distribution of Willow Flycatchers throughout the region is already being used to inform and prioritize conservation and restoration activities to benefit the species.
Mathewson, H.A., M.L. Morrison, H.L. Loffland, and P.F. Brussard. 2012. Ecology of willow flycatchers (Empidonax traillii) in the Sierra Nevada, California: effects of meadow characteristics and weather on demographics. Ornithological Monographs 75:1-31. PDF
Siegel, R.B., R.L. Wilkerson, and D.F. DeSante. 2008. Extirpation of the Willow Flycatcher from Yosemite National Park. Western Birds 39:8-21. PDF
Bombay, H.L., M.L. Morrison, and L.S. Hall. 2003. Scale perspectives in habitat selection and animal performance for Willow Flycatchers (Empidonax traillii) in the central Sierra Nevada, California. Studies in Avian Biology 26:60-72. PDF
Strohm, K.H., and H.L. Loffland. 2015. 2015 Willow Flycatcher Surveys in the Tahoe National Forest. The Institute for Bird Populations, Point Reyes Station, CA. PDF
Loffland, H L., and R.B. Siegel. 2014. 2014 Willow Flycatcher surveys in east-side meadows on the Tahoe National Forest. The Institute for Bird Populations, Point Reyes Station, CA. PDF
Loffland, H.L., R.B. Siegel, C. Stermer, B.R. Campos, R.D. Burnett, and T. Mark. 2014. Assessing Willow Flycatcher population size and distribution to inform meadow restoration in the Sierra Nevada and Southern Cascades. The Institute for Bird Populations, Point Reyes Station, CA. PDF
Siegel, R.B., R.L. Wilkerson, and D.F. DeSante. 2007. Determining the status and distribution of Willow Flycatcher in Yosemite National Park. Report to Yosemite National Park. The Institute for Bird Populations, Point Reyes Station, CA.
Bombay, H.L., T.M. Benson, B.E. Valentine, and R.A. Stefani. 2003. A willow flycatcher survey protocol for California. U.S.D.A. Forest Service. PDF
Albert, S. 2002. Tribal perspectives on southwestern Willow Flycatcher management and the Endangered Species Act. Pages N1-N21 in: Final recovery plan, southwestern Willow Flycatcher, Appendix N. PDF