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Soil Investigations for Data Collection in the Delta Initial Study/Proposed Mitigated Negative Declaration 63 around each burrow being used during the nonbreeding season. The buffers will be delineated by highly visible, temporary fencing or flagging. Ferruginous Hawk (Buteo regalis) Ferruginous Hawk is a USFWS Bird of Conservation Concern. The species is a large, broad-winged hawk with a large head and pale underparts with rusty legs that form a V when soaring. Ferruginous Hawks range from breeding grounds in southern Canada to wintering grounds in Mexico. They overwinter in California in grasslands and agricultural areas, including sagebrush flats, desert scrub, low foothills surrounding valleys, and fringes of pinyon-juniper habitats. Ferruginous Hawk forages in open, dry grassland habitats (Polite and Pratt 1999, Ng et al. 2017), also in open cultivated lands such as grain and hay crops, recently plowed fields, and pastures. Nesting has not been recorded in California (CDFW 1999b). Ferruginous Hawk is regularly observed in the winter, suitable foraging habitat is present in the Study Area, and several occurrences have been documented within 0.5 to 3 miles of Impact Areas, however no nesting occurs in California. Therefore, Ferruginous Hawk has a moderate potential to occur within the Study Area. Implementation of Mitigation Measures MM BIO-1 and MM BIO-6 would reduce potential impacts to Ferruginous Hawk to: Less than Significant with Mitigation Incorporated. Swainson’s Hawk (Buteo swainsoni) Swainson's Hawk is listed as Threatened under CESA. Swainson’s Hawk is a medium-sized hawk with tapered wings that have contrasting light wing lining and dark flight feathers (Bechard et al. 2010). It migrates from Central and South America to breed in western North America, primarily in California and the Great Basin. The Central Valley breeding population largely winters from Mexico to central South America (Hull et al. 2008). Foraging habitat includes hay and alfalfa fields, grassland, pastures, grain crops, and row crops; nesting occurs in mature riparian woodland, roadside or isolated trees near foraging habitat; trees in urban or rural neighborhoods are also used (Estep 1984, Schlorff and Bloom 1984, England et al. 1997). Swainson’s Hawk forages in large open habitats, such as hay and alfalfa fields, pastures, grain crops, and row crops primarily for small mammals such as voles, but will opportunistically take invertebrates, small birds, and reptiles. The species is monogamous and exhibits strong site fidelity to nesting territories, occupying the same sites over many years (Hull et al. 2008). Breeding occurs from late March to late August, with peak activity from late May through July (CDFW 2006). Swainson’s Hawk has a high potential to occur within the Study Area, as suitable foraging and nesting habitat occurs in many locations within the Study Area and there are many reported occurrences. Implementation of Mitigation Measures MM AES-1, MM BIO-1 and MM BIO-11 would reduce potential impacts to Swainson’s Hawk to: Less than Significant with Mitigation Incorporated.