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I I I I I I I I I I I I I I I t I I I BIOLOGICAL OPINION Status of the Species flycatcher's range. Table 4 presents data on nest heights in different riparian habitat types across the flycatcher's range. Southwestern willow flycatcher nests have been found as low as 0.6 m above the ground to 14 m above the ground. The data presented in Table 4 demonstrate that flycatchers that use predominantly native broadleaf riparian habitats place their nests relatively low to the ground (between 1.8 m and 2.1 m on average), whereas those using mixed native/exotic and monotypic exotic riparian habitats place their nests relatively high above the ground (between 4.3 m and 7.4 m on average). Historic egg/nest collections and species' descriptions from throughout the southwestern willow flycatcher I s range confirm the bird' s widespread use of willow for nesti ng (Phillips 1948, Phillips et al. 1964, Hubbard 1987, Unitt 1987, T. Huels in lilt. 1993, San Diego Natural History Museum 1995). Of the 34 nests found by Brown in 1902 near Yuma on the lower Colorado and Gila rivers, 33 were in Goodding's willow and one was in arrowweed. Data from historic egg collections from southern California and more current studies indicate that 75 to 80% of nests were placed in willows (San Diego Natural History Museum 1995). Currently, southwestern willow flycatchers use a wide variety of plant species for nesting substrates. At the monotypic willow stands that characterize high elevation sites in Arizona, Geyer willow was used almost exclusively for nesting (Muiznieks et al. 1994) and on the Colorado River, Gooding's willow was the primary nesting substrate (R. McKernan unpubl. data). Along a 20-mile stretch of the Gila River in Grant County , New Mexico, where boxelder is the dominant understory species, 76% of flycatcher nests were placed in boxelder, with the remainder in Russian olive and saltcedar (Skaggs 1996). At the inflows of Tonto Creek and Salt River to Roosevelt Lake in Gila County, Arizona, both of which are comprised of monotypic stands of saltcedar, 100% of flycatcher nests were placed in saltcedar (Muiznieks et al. 1994, Sferra et al. 1995, Spencer et al. 1996, Corman et al. 1996). On the San Luis Rey River in San Diego County, California, approximately 90% of flycatcher nests were placed in live oak (Quercus agrifolia), typically an upland species, which became the dominant plant species adjacent to the stream after willows were removed in the 1950s as a water conservation measure and a reservoir upstream reduced flood frequency and streamflow volume (San Diego Natural History Museum 1995, W.Haas, pers. comm.). Other plant species where southwestern willow flycatcher nests have been documented include: buttonbush, black twinberry (Lonicera involucrata), Fremont cottonwood, white alder (Alnus rhombifolia), blackberry (Rubus ursinus), Russian olive, and Salix hindsiana. 53