The Willow Flycatcher (Empidonax traillii) was formerly a common summer resident in California, breeding in riparian willow thickets. It has been extirpated from most of its California range and is currently under consideration for state Threatened or Endangered status (R. Schlorff, pers. comm.).
Most of the remaining populations occur in isolated mountain meadows of the Sierra Nevada and along the Kern, Santa Margarita, and San Luis Rey rivers (Remsen 1978; Serena 1982; Unitt 1987). The California Department of Fish and Game conducted a survey for Willow Flycatchers in six Sierra Nevada national forests and Yosemite National Park in 1982 (Serena 1982).