Willow Flycatcher (Empidonax traillii)

Threats

The Willow Flycatcher has declined precipitously in the Sierra Nevada since the middle of the twentieth century. Once considered common throughout much of the Sierra Nevada, the Sierra population was estimated to have dwindled to just 300-400 individuals in the late 1990s. Willow flycatcher populations across the West are facing serious declines based largely upon habitat loss and destruction.

The loss of dense willow in meadows is probably the principal reason for the reduction of Willow flycatcher population and the contraction of its range. This loss of meadow habitat leads directly to poor nesting success due to lack of nesting habitat and also because this reduction allows predators easier access to Willow flycatcher nests. The degradation of meadow habitat is also a major problem for the species and this arises from trampling by livestock, road construction, recreation activities, adjacent timber harvests or fuels treatments, fire suppression, water diversions, mining, lodgepole pine encroachment, water diversion and hydroelectric development, and climate change.

Inappropriate and excessive livestock grazing directly impact Willow flycatcher populations and habitat by knocking over nests in willow thickets, altering the vegetation and hydrology of montane meadows, consuming the lower branches and shrub layers of streamside vegetation, consuming or trampling young riparian plants, reducing water quality, compacting soils, and accelerating streambank erosion.

Cowbird parasitism is also a significant threat to the Willow flycatcher due to its tendency to lay eggs in Willow flycatcher nests. Once this egg hatches the young cowbird forces the eggs of the Willow flycatcher or newly hatched young out of the nest.

Habitat

Willow flycatchers require standing or running water near dense large patches of willow for breeding (USDA 2001 SNFPA pg.144 ). In the Sierra Nevada, Willow flycatchers are found only in meadows that contain willows and alders.

Conservation

Wet meadows of the Sierra Nevada are a critical resource for the rare Willow Flycatcher and for many other breeding birds. These meadows are typically man-aged for livestock production, often to the detriment of wildlife. Fencing stream and meadow areas to prevent the entry of cattle on these sensitive lands, coupled with monitoring and restoration, and in some cases removal of cows, as provided in the original Sierra Nevada Framework of 2001, are sound protection measures to help Willow Flycatcher populations survive. The Framework revisions of 2004 removed many of the restrictions on grazing, increased grazing in some cases, and does not provide the protection needed to allow this species to recover. The critical status of the willow flycatcher warrants reducing or excluding livestock grazing and other land uses adversely affecting montane meadows and riparian habitat, particularly where there are known flycatcher territories, unless new research can show the land uses have no detrimental effects on the flycatcher and other species. Developments which attract cowbirds such as campgrounds should be kept away from riparian areas to minimize the impacts of the cowbirds on Willow flycatchers and other species nesting in willow thickets of mountain meadows.

Status

The Willow flycatcher is a Forest Service sensitive species, a U.S. Fish and Wildlife Service species of concern, and has been listed as an endangered species by the State of California since 1990. Currently, half of the California breeding population of the Willow flycatcher is in the Sierra Nevada. According to the USFS, the Sierran subspecies of the willow flycatcher has the highest priority for conservation because of their high potential for extirpation from the Sierra (USDA 2001 SNFPA pg.143). Meadow habitat loss is a primary threat to this subspeices (Harris et al 1986; Valentine et al. 1988; USDA SNFPA 2001). Forests currently with the species as a management indicator species are the Eldorado, Modoc, Sierra, Stanislaus, and Tahoe National Forests and the Lake Tahoe Basin Management Unit.