Restoration Potential: Has become so rare in the southwest and California that extirpation from many remaining breeding areas seems likely without dramatic management efforts and habitat restoration. Elsewhere in the West, riparian and meadow restoration is needed to sustain the species and reverse declining trends. Fortunately, riparian and willow habitats are resilient where natural hydrologic dynamics and native vegetation are restored. Where cowbirds are affecting population viability, measures to reduce cowbird presence during the breeding season will be needed. Less is known about the restoration needs in the eastern and northwestern portions of its range, but these populations currently seem somewhat more abundant and stable.
Preserve Selection and Design Considerations: Minimum area requirements and patch dynamics are still largely unknown. Small openings in deciduous shrub habitats or adjacent stream edges increase habitat suitability, and large, contiguous willow patches apparently do not support willow flycatchers at the interior of the patch (USDA Forest Service 1994). In California montane meadows, the smallest documented nesting area is a 0.25 hectare meadow in the Sierra Nevada, but other observers found most nesting territories in meadows greater than 8.0 hectares and none in meadows less than 0.4 hectares (USDA Forest Service 1994). For southwestern willow flycatcher (E. T. EXTIMUS), patches as small as 0.5 hectares have been found to support one to two pairs, and habitat patches range from 0.5 to 1.2 hectares (USFWS 1995).
Management Requirements: HABITAT MANAGEMENT: Will benefit from maintaining communities of deciduous shrubs in riparian areas and meadows, with patches of dense shrubs interspersed with openings, and with open water nearby. In areas where populations have declined, existing breeding areas should be protected from habitat loss. It should be noted that unoccupied sites are not necessarily unsuitable, as populations may be dynamic (Harris et al. 1987).
In the Sierra Nevada, needs riparian areas and wet meadows at least 0.25 hectares in size with openings and large, dense patches of deciduous shrubs, and dense foliage at mid-heights (1-2 meters); habitat areas of at least 8 hectares are optimal. Territories contained 5-80 percent willow (SALIX spp.) cover (average 44 percent), 18-78 percent (average 54 percent) foliage density in the 0-1 meter shrub layer, and 45-96 percent (average 69 percent) foliage density in the 1-2 meter shrub layer (Sanders and Flett 1989).
Management recommendations for montane meadows include: (1) maintain riparian deciduous shrubs at least 1-2 meters high in patches greater than 0.1 hectares (100 square meters); (2) maintain more than 40 percent foliage cover density in lower 2 meters of the deciduous shrub layer; (3) maintain shrub patches interspersed with openings, and opening or paths should be at least 2 meters wide to allow aerial foraging (USDA Forest Service 1994).
Critical habitat areas containing the remaining known populations of southwestern willow flycatcher (E. T. EXTIMUS) were identified by the U.S. Fish and Wildlife Service in Southern California, Arizona, and New Mexico (USFWS 1997a, 1997b). In Arizona, habitat recommendations include: (1) establish a "no net loss" policy; increasing suitable riparian habitat and promoting regeneration of native plants; (2) using buffer zones between riparian habitats and adjacent developments; (3) restore connectivity of natural reaches of habitat by restoring degraded segments; (4) establish areas of slow water and backwater; (4) manage for large contiguous habitat blocks rather than isolated fragments (Latta et al. 1999). Also see Deshler et al. (1997) for an extensive bibliography on this subspecies.
WATER MANAGEMENT: The species requires saturated soils, standing water or flowing water near nesting sites. Natural flooding and channel meandering can promote native riparian vegetation communities. Maintaining wetlands and wet meadows will help sustain willow communities. Arizona recommendations include: managing water diversions and groundwater withdrawal to maintain streamside vegetation and mimic natural stream flow regimes, including periodic floods (Latta et al. 1999).
GRAZING: In Oregon, populations dramatically increased after reducing cattle grazing and ceasing the poisoning and removal of riparian willows (Taylor and Littlefield 1986). Reducing or eliminating grazing during the nestling period would reduce direct damage by livestock (USDA Forest Service 1994). Flycatchers will nest near cattle trails (Sanders and Flett 1989), and in some circumstances cattle might be used to create trails and openings in exceptionally dense willow stands (outside the breeding season) to benefit flycatchers. Livestock management recommendations include: (1) eliminate livestock use during the breeding period from early June to mid-August; (2) manage stocking rates and timing to encourage riparian shrub growth and vigor; (3) use exclosures to protect sensitive areas from browsing and soil compaction (USDA Forest Service 1994).
BROOD PARASITES: Eliminating livestock in breeding habitat during the breeding season can help alleviate cowbird brood parasitism. Cowbird trapping and control is intensive, expensive, and must be ongoing to be effective. However, control efforts on two sites in California in the early 1990s helped conserve isolated populations, stabilizing numbers at one site and increasing nest success at the other (USFWS 1996). Management recommendations to reduce the impacts of cowbirds include: (1) manage livestock to prevent aggregations near breeding habitat during nest building, egg-laying and incubation, late May to late July; (2) ideally, corrals, pack stations, and other facilities that concentrate stock should be 5 to 10 kilometers from important habitat areas, and at least 1 kilometer from nest sites; (3) implement cowbird trapping if necessary in coordination with state fish and wildlife agencies (USDA Forest Service 1994). In Arizona, recommendations include: reducing parasitism rates to less than 20 percent; monitoring nests; implementing trapping programs where parasitism rates exceed 20 percent (Latta et al. 1999).
Management Research Needs: Details of habitat and management needs in the eastern extent of its range are largely unknown. Where populations are depleted in the West, annual population and productivity monitoring is needed as well as surveys to determine presence/absence, distribution, and habitat relationships. Information is needed on landscape relationships, minimum area requirements, patch dynamics; also effect of breeding habitat isolation and connectivity. Further study is needed of habitat preferences throughout the species range, particularly in relation to productivity, use of non-native vegetation, relationship to land management activities, and response of flycatchers to habitat restoration. More information is needed on parasitism rates, productivity of parasitized nests, response to parasitism, and activities and habitat that promote the incidence of cowbirds. Effects of pesticides on the species are unknown. Information on winter habitat use, winter ecology, and threats on the wintering grounds are almost entirely lacking.
Biological Research Needs: Many aspects of the taxonomy, biology and ecology remain unstudied. Diet composition, winter habits and ecology are unknown. Genetic studies of subspecies are needed. Migration patterns and the location of wintering sites for different subspecies remain unknown, largely due to the difficulty of distinguishing the species outside the breeding season. Demographics (productivity and survivorship) need further study, especially in relation to habitat quality and to landscape variables at different scales. Variation in songs and calls across the species range and among subspecies need study.