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Mature riparian vegetation along the west levee of the Sacramento River provides suitable nesting habitat for Swainson's hawk, and May-June 2001 surveys confirmed that there are active nests in the habitat along the levees, but outside of construction area boundaries. The suitability of this habitat for Swainson's hawk nesting was confirmed in a March 29, 2004 field tour, which noted that there had been no change in the overall condition of levee riparian habitats since 2001. During a March 30, 2005 survey, 4 pairs of Swainson's hawks were observed flying and vocalizing between the Boyers Bend Pumping Plant and the Tyndal Mound Pumping Plant, but it was too early to determine which trees in this reach if any) would be selected as nest sites. Additional survey is planned for 2005. 3.4.4.9 Giant Garter Snake (Thamnophis gigas) (FT/CT) Giant garter snakes (Thamnophis gigas) (FT/CT) historically inhabited the marshlands that covered a large portion of the Sacramento and San Joaquin valleys. Giant garter snakes are associated with aquatic environments that contain: 1) sufficient water during the active (summer) season to supply food (fish and amphibians) and cover, 2) vegetated banks for basking located immediately adjacent to water, 3) emergent vegetation for cover during the active season, and 4) high ground or uplands, such as levees or railroad grades, that provide cover and refugia from floodwaters during the dormant (winter) season (Hansen 1988, Hansen and Brode 1993). Giant garter snakes appear to be absent from most permanent waters that support predatory introduced bass, sunfish, and catfish that compete with giant garter snakes for prey and likely prey upon the snake as well (Hansen 1988). The widely introduced bullfrog (Rana catesbeiana) also has been shown to prey upon garter snakes (Treanor 1983); young snakes may be particularly vulnerable to bullfrog predation. This species also appears to be absent from natural or artificial waterways that undergo routine mechanical or chemical weed control or compaction of bank soils (Hansen 1988, Hansen and Brode 1993). The conversion of marsh lands to agriculture and the construction of flood control levees is probably the most significant cause of adverse effects to the giant garter snake. In 1999, a draft recovery plan for giant garter snake was prepared, but it has not been finalized. USFWS and CDFG are engaged in conservation efforts for the species in nearby Placer and Sacramento Counties, focusing on the maintenance of areas of suitable upland habitat connected by irrigation canals. The Natomas Basin Habitat Conservation Plan (HCP) also provides for conservation efforts in Sacramento County along the southern border of Sutter County. The MSCS "r" goal for the species is to "Protect the existing population and habitat within the Delta Region; restore, enhance, and manage suitable habitat areas adjacent to known populations to encourage the species to expand naturally.” Giant garter snakes have been recorded at three locations on the west side of the Sacramento River within a 10-mile radius of the project area (occurrences 19, 117, and 158 in CNDDB 2005). Occurrence 19 was a single giant garter snake observed in 1976 in the vicinity of Sycamore Slough, 0.6 miles east of Road 95B by G. Hansen. This location is approximately 4 miles south of the Combined Pumping Plant and Fish Screen, 0.5 miles from the southern end of the canal construction area at Tyndal Mound Pumping Plant, and about 2 miles north of the Main Drain borrow site. During subsequent studies in 1986-1987 by G. Hansen, no giant garter snakes were observed. Occurrence 117 was a single giant garter snake observed by G. Hansen adjacent to the Colusa Basin Drainage Canal CBD Canal), about 1.5 miles southwest of the Main Drain borrow site. In 2003 and 2004, the U.S. Geological Survey conducted live-trapping and radio-telemetry studies of giant garter snakes in the CBD Canal, capturing 82 snakes in 2003 and 46 snakes in 2004 (USGS 2004). All of the giant garter snakes captured were associated with aquatic and/or bank-side habitats in the CBD Canal or adjacent rice fields to the south. In 2004, sixteen giant garter snakes were fitted with radio transmitters. Of these 16 snakes, (a) 1 died within a day of release, (b) 8 stayed in or near to the CBD Canal, (b) 7 moved to the rice fields south of the CBD Canal and used those fields as summer habitat. Four of the 7 snakes that used rice fields as summer habitat remained there to the end of October and the rest returned to the CBD Canal. There was high variation in the distance moved by the transmitter-fitted snakes and estimates of home ranges ranged from 0.4 hectares to 3744 hectares (1.0 to 9248 acres). None of the transmitter-fitted snakes moved north of the CBD Canal. Occurrence 158 was a single giant garter snake observed in 2001 about 150 feet (45 meters) from a vegetated drainage ditch along White Road, between the CBD Canal and the Main Drain. There were rice fields present in the surrounding area. This site is about 1.5 miles from the northernmost portion of the proposed canal improvements for the Proposed Project. Along the levee landside base of the levee, the concrete-lined channels proposed for reconfiguration lack emergent vegetation, prey base, burrows and crevasse suitable for refugia, and adjacent supporting upland habitats. Adjacent crops are row crops, including wheat and alfalfa. The segment of new canal proposed from the Combined Pumping Plant and Fish Screen facility to Boyers Bend will cross a field currently in wheat before crossing under Highway 45 and connecting to an existing concrete-lined canal. The borrow site west of Highway 45 is a wheat field. The Combined Pumping Plant and Fish Screen is isolated from any suitable giant garter snake habitat by (a) Highway 45, (b) a wide band of field crops, and (c) the existing concrete-lined canals and their unpaved access roads. None of these areas has suitable giant garter snake habitat or connectivity to such habitat. The Main Drain represents the only potential supporting habitat for giant garter snakes, and connectivity of this habitat to project construction areas is limited to the area adjacent to the borrow site along the Main Drain, southwest of Tyndall Mound Pumping Plant. In this segment of the Main Drain, habitat is of marginal quality and there is no hydrologic connection between this area and the giant garter snake population in the CBD Canal, which is isolated from the farmland to the north by a levee. Connectivity to the known population in the CBD Canal would require overland movement across approximately 1-mile of agricultural fields, planted in row crops. There remains some potential for individual giant garter snakes to use the Main Drain as a transit corridor and could move into local farm drain systems during irrigation, particularly during flooding of rice fields west of the borrow site. However, fluctuating water levels limit emergent vegetation in the Main Drain, the banks are steep, and there is little cover along the wide raised levee along the north side of the Main Drain, portions of which will be removed for use in construction. 3.4.4.10 Valley Elderberry Longhorn Beetle (Desmocerus californicus dimorphus) (FT) The valley elderberry longhorn beetle (Desmocerus californicus dimorphus) is a medium-sized (about 2 cm long) beetle. The forewings of the female are dark metallic green with red margins; those of the male are red with dark green spots. This species is associated with habitats that support elderberry (Sambucus spp.), its exclusive host plant. Adult valley elderberry longhorn beetles lay eggs upon the plants, after which larvae bore in and excavate pupal cells. After pupation, new adults emerge leaving a characteristic emergence or "exit hole" and use elderberry for resting, foraging, and mating. The presence of exit holes in elderberry stems is the accepted measure of valley elderberry longhorn beetle presence and habitat use. In addition, all elderberry shrubs within the known range of the valley elderberry longhorn beetle and having a stem diameter of one inch or greater at ground level are considered potential habitat and are protected under the Federal ESA. The valley elderberry longhorn beetle is listed as Federally threatened. There are no recovery efforts in the Action Area or immediately adjacent areas. The MSCS "r" goal for the species is to "Maintain and restore connectivity among riparian habitats occupied by the valley elderberry longhorn beetle and within its historical range along the Sacramento and San Joaquin rivers and their major tributaries." USFWS and California DWR are replanting elderberry along the American River, about 40 miles from the project site. USFWS reports some success with transplanting inhabited trees. Adult valley elderberry longhorn beetles and/or exit holes have been reported from several locations along the Sacramento River as far north as Redding. The closest recorded occurrence of valley elderberry longhorn beetle to the Action Area is along the Sacramento River, between Knight's Landing and the Feather River (NDDB 2004). Elderberries are a native component of the riparian ecosystem along the Sacramento River. They typically grow along the higher terrace and are intermixed with poison oak and other riparian shrubs. All elderberry shrubs identified during 2001 and 2005 surveys are more than 50 feet (15 meters) outside of the footprint of the Proposed Project; stems were not measured and bushes were not checked for exit holes. May and June 2001 surveys found elderberry bushes suitable for the valley elderberry longhorn beetle at 5 locations (Table 3-5). Table 3-5. Elderberry shrubs in the study area (May and June 2001 Surveys, Green 2001, and Green 2005).
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