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. . Area Manager DRAFT 23 mulefat; Baccharis spp.), boxelder (Acer negundo), stinging nettle (Urtica spp.), blackberry (Rubus spp.), cottonwood (Populus spp.), arrowweed (Tessaria sericea), tamarisk (aka saltcedar; Tamarix ramosissima), and Russian olive (Eleagnus angustifolia) (Grinnell and Miller 1944, Phillips et al. 1964, Hubbard 1987, Whitfield 1990, Brown and Trosset 1989, Brown 1991, Sogge et al. 1993, Muiznieks et al. 1994, Maynard 1995, Cooper 1996, Skaggs 1996, Cooper 1997, McKernan and Braden 1998, Stoleson and Finch 1999, Paradzick et al. 1999). Habitat characteristics such as plant species composition, size and shape of habitat patch, canopy structure, vegetation height, and vegetation density vary across the subspecies' range. However, general unifYing characteristics of flycatcher habitat can be identified. Regardless of the plant species composition or height, occupied sites usually consist of dense vegetation in the patch interior, or an aggregate of dense patches interspersed with openings. In most cases this dense vegetation occurs within the first 3 to 4 m (10 to 13 ft) above ground. These dense patches are often interspersed with small openings, open water, or shorter/sparser vegetation, creating a mosaic that is not uniformly dense. In almost all cases, slow-moving or still surface water and/or saturated soil is present at or near breeding sites during wet or non-drought years. Thickets of trees and shrubs used for nesting range in height from 2 to 30 m (6 to 98 ft). Lower- stature thickets (2 to 4 m or 6 to 13 ft) tend to be found at higher elevation sites, with tall stature habitats at middle and lower elevation riparian forests. Nest sites typically have dense foliage from the ground level up to approximately 4 m (13 ft) above ground, although dense foliage may exist only at the shrub level, or as a low dense canopy. Nest sites typically have a dense canopy, but nests may be placed in a tree at the edge of a habitat patch, with sparse canopy overhead. The diversity of nest site plant species may be low (e.g., mono cultures of willow or tamarisk) or comparatively high. Nest site vegetation may be even- or uneven-aged, but is usually dense (Brown 1988, Whitfield 1990, Muiznieks et al. 1994, McCarthey et al. 1998, Sogge et al. 1997a, Stoleson and Finch 1999). Historically, the flycatcher nested in native vegetation, such as willows, buttonbush, boxelder, and Baccharis, sometimes with a scattered overstory of cottonwood (Grinnell and Miller 1944, Phillips 1948, Whitmore 1977, Unitt 1987). Following modern changes in riparian plant communities, the flycatcher still nests in native vegetation where available, but also nests in thickets dominated by the non-native tamarisk and Russian olive and in habitats where native and non-native trees and shrubs are present in essentially even mixtures (Hubbard 1987, Brown 1988, Sogge et al. 1993, Muiznieks et al. 1994, Maynard 1995, Sferra et al. 1997, Sogge et al. 1997a, Paradzick et al. 1999). Although the quality of exotic species such as saltcedar as nesting habitat for flycatchers has been debated, comparisons of reproductive performance (U.S. Fish and Wildlife Service 2002a) and physiological conditions (Owen and Sogge 2002) of flycatchers breeding in native and exotic vegetation have revealed no differences. Open water, cienegas, marshy seeps, or saturated soil are typically in the vicinity of flycatcher territories and nests. Flycatchers sometimes nest in areas where nesting substrates are in standing water (Maynard 1995; Sferra et al. 1995, 1997). However, hydrological conditions at a particular site can vary greatly in the arid Southwest within a season and among years. Also, because riparian vegetation typically occurs in flood plain areas that are prone to periodic disturbance, suitable habitats will be ephemeral, with a dynamic distribution (U.S. Fish and Wildlife Service 2002). Suitable habitat patches may become unsuitable through maturation or