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Soil Investigations for Data Collection in the Delta Initial Study/Proposed Mitigated Negative Declaration 74 mulefat (Baccharis salicifolius) and other mesic species (Goldwasser 1981; Gray and Greaves 1981; Franzreb 1989). Oak woodland with a willow riparian understory is also used in some areas (Gray and Greaves, 1981), and individuals sometimes enter adjacent chaparral, coastal sage scrub, or desert scrub habitats to forage (Kus et al 2010). Foraging occurs most frequently in willows (Salata 1983; USFWS 1998a) but occurs on a wide range of riparian species and even some nonriparian plants that may host relatively large proportions of large prey (USFWS 1998a). Least Bell’s Vireos are insectivorous and prey on a wide variety of insects, including bugs, beetles, grasshoppers, moths, and especially caterpillars (Chapin 1925; Bent 1950). Breeding occurs between April and August, with peak egg laying in May to early June (CDFW 1990h). Least Bell’s Vireo has a moderate potential to occur within the Study Area due to the presence of suitable nesting habitat in the Study Area, and recent observations of the species in the Yolo Bypass Wildlife Area and Bradford Island during breeding season. Implementation of Mitigation Measures MM AES-1, MM BIO-1 and MM BIO-8 would reduce potential impacts to Least Bell’s Vireo to: Less than Significant with Mitigation Incorporated. Yellow-Headed Blackbird (Xanthocephalus xanthocephalus) Yellow-Headed Blackbird is a California species of special concern. Yellow- Headed Blackbird is a large blackbird with large head and long conical bill; males have a bright yellow head and breast and glossy black body and females are brown with dull yellow head and breast. The species’ range includes western and central North America; in California it is found in northeastern California, Central Valley, Imperial Valley, and Colorado River Valley (Jaramillo 2008). Yellow- Headed Blackbird breeding habitat includes freshwater emergent wetlands, while associated foraging habitat includes irrigated pastures and alfalfa fields (Twedt and Crawford 1995, Jamarillo 2008). The species forages primarily for seeds and some insects; during breeding season insects are the primary prey (Jaramillo 2008). Nests are constructed in tall emergent vegetation in open areas over relatively deep water (Orians and Willson 1964). Breeding occurs from mid-April through late July (Twedt and Crawford 1995). Yellow-Headed Blackbird has a moderate potential to occur within the Study Area due to the presence of suitable foraging habitat and minimal suitable nesting habitat in the Study Area. Implementation of Mitigation Measures MM BIO-1 and MM BIO-8 would reduce potential impacts to Yellow-Headed Blackbird to: Less than Significant with Mitigation Incorporated. Antioch Dunes anthicid beetle (Anthicus antiochensis) Antioch Dunes anthicid beetle has a NatureServe ranking of G1S1 and is included on CDFW’s Special Animals List but is not listed under FESA or CESA. This species is a 4.7-5.4 mm long terrestrial beetle that resembles an ant in appearance. It is endemic to California, and it has been detected at Antioch