C.4 Avian Study Summary of Results

Transcription

1 C.4 Avian Study Summary of Results

2 Avian Baseline Studies for the Alta-Oak Creek Mojave Wind-Energy Project Kern County, California Summary of Results February 4 July 11, 2009 Prepared for: CH2M HILL Prepared by: Wallace Erickson and Andrea Chatfield Western EcoSystems Technology, Inc Central Avenue Cheyenne, Wyoming WEST, Inc. July 15, 2009

3 Western EcoSystems Technology, Inc. initiated surveys and monitoring of avian resources within the proposed Alta-Oak Creek Mojave Wind-Energy Project (Project) in Kern County, California, in February of The study area consists of three distinct subareas known as CPC East, CPC Proper, and Ward. The following document contains a summary of results for fixedpoint avian use surveys, raptor nest surveys, and burrowing owl surveys within each subarea. The objective of the fixed-point bird use surveys was to estimate the seasonal, spatial, and temporal use of the by birds, particularly raptors (defined here as kites, accipiters, buteos, harriers, eagles, falcons, or owls). Fixed-point bird use surveys were conducted from February 4 th to June 30 th, Nineteen points were established within the Project including 10 points within CPC Proper, eight points within CPC East, and one point within Ward. Each point was visited weekly during the winter (February 4 February 28), spring (March 1 May 31), and summer (June 1 June 30), for a total of 418 thirty-minute surveys. Avian Use Surveys CPC East Within CPC East, a total of 2,914 individual birds within 954 separate groups were recorded during fixed-point bird use surveys, representing a total of 68 species (26 in winter, 62 in spring and 24 in summer). Passerines comprised 82.6% of observations, and raptors accounted for 0.4% of all bird observations. A total of 13 raptors comprising five species were recorded during fixedpoint surveys, with red-tailed hawk (Buteo jamaicensis) and prairie falcon (Falco mexicanus) accounting for the majority of observations (five and four individuals, respectively). Overall, passerines were the most abundant bird type observed in winter (11.98 birds/plot/30-min. survey), spring (13.17), and summer (3.86). Of the large bird types observed, large corvids (common raven [Corvus corax])) were the most abundant bird type observed in winter (1.70 birds/plot/30-min. survey) and summer (0.3), while vultures were the most abundant in spring (1.22). Seasonal raptors use was greatest in winter and summer (0.10 birds/plot/30-min. survey during both seasons) compared to spring (0.03). During the bird use surveys, 695 single birds or groups totaling 2,295 individuals were observed flying. Of the large bird types observed, 82.3% were flying below the likely zone of risk (ZOR) for potential collision with a turbine blade, 9.9% were within the ZOR, and 7.8% were observed flying above the ZOR for typical turbines that could be used in the Project. Of the small bird types observed, 99.4% were flying below the ZOR, 0.6% were within the ZOR, and none were above the ZOR. The bird type most often observed flying within the turbine zone of risk was raptor (33.3%). For species with at least 10 separate observations of flying birds, those most often observed within the zone of risk were turkey vulture (Cathartes aura; 89.0%) and common raven (20.8%). Based on the use (measure of abundance) of the site by each species and the flight characteristics observed for that species, common raven had the highest probability of turbine exposure, followed by turkey vulture and house finch (Carpodacus mexicanus). Three state species of concern were recorded within CPC East: loggerhead shrike (45 individuals), Le Conte s thrasher (Toxostoma lecontei; 21 individuals), and northern harrier (Circus cyaneus; one individual). Additionally, two golden eagles (Aquila chrysaetos) were Western EcoSystems Technology, Inc. 2 July 15, 2009

4 recorded during surveys. The golden eagle does not have endangered, threatened, or species of concern status, but it is legally protected under the Bald and Golden Eagle Protection Act, and is a fully protected species in California. CPC Proper Within CPC Proper, a total of 3,808 individual birds within 1,071 separate groups were recorded during fixed-point bird use surveys, representing a total of 93 species (35 in winter, 81 in spring and 41 in summer). Passerines comprised 75.2% of observations, and raptors accounted for 1.3% of all bird observations. A total of 49 raptors comprising six species were recorded during fixedpoint surveys, with red-tailed hawk accounting for the majority of observations (31 individuals). Overall, passerines were the most abundant bird type observed in winter (14.28 birds/plot/30- min. survey), spring (19.51), and summer (9.15). Of the large bird types observed, large corvids were the most abundant bird type observed in winter (2.44 birds/plot/30-min. survey), spring (4.18), and summer (3.45). Seasonal raptors use was greatest in winter (0.41 birds/plot/30-min. survey) compared to spring (0.26) and summer (0.23). During the bird use surveys, 749 single birds or groups totaling 3,145 individuals were observed flying. Of the large bird types observed, 79.1% were flying below the likely ZOR for potential collision with a turbine blade, 17.3% were within the ZOR, and 3.6% were observed flying above the ZOR. Of the small bird types observed, 99.3% were flying below the ZOR, 0.6% were within the ZOR, and 0.4% were above the ZOR. Bird types most often observed flying within the turbine zone of risk were vultures (72.7%), followed by raptors (53.3%). For species with at least 15 separate observations of flying birds, those most often observed within the zone of risk were red-tailed hawk (71.4%) and common raven (55.8%). Based on the use (measure of abundance) of the site by each species and the flight characteristics observed for that species, common raven had the highest probability of turbine exposure, followed by red-tailed hawk and horned lark (Eremophila alpestris). One state endangered species was observed during surveys within CPC Proper: willow flycatcher (Empidonax traillii; three individuals; Figure 2). The southwestern subspecies (E. t. extimus), which has federal endangered status in addition to the state listing, breeds in southern California, while the little willow flycatcher (E. t. brewsteri) breeds on the west side of the Sierra Nevada. It is not known which subspecies was observed during surveys, as both species are potential migrants through the area in May and June. There was no indication that the willow flycatchers observed were breeding in the area, and were more likely migrants passing through the region. Four state species of concern were recorded within CPC Proper: loggerhead shrike (Lanius ludovicianus; six individuals), yellow warbler (Dendroica petechia), olive-sided flycatcher (Contopus cooperi; one individual), and tricolored blackbird (Agelaius tricolor; five groups comprising 199 individuals). Additionally, five golden eagles were recorded during surveys. Ward Within Ward, a total of 360 individual birds within 140 separate groups were recorded during fixed-point bird use surveys, representing a total of 24 species (11 in winter, 19 in spring and 12 in summer). Passerines comprised 81.9% of observations, and raptors accounted for 1.7% of all bird observations. A total of six raptors were recorded during fixed-point surveys, all of which were red-tailed hawks. Overall, passerines were the most abundant bird type observed in winter Western EcoSystems Technology, Inc. 3 July 15, 2009

5 (6.75 birds/plot/30-min. survey), spring (12.85), and summer (20.20). Of the large bird types observed, large corvids were the most abundant bird type observed in winter (0.75 birds/plot/30- min. survey), spring (2.00), and summer (2.40). Seasonal raptors use was greater in spring (0.38 birds/plot/30-min. survey) than in summer (0.20); no raptors were observed during winter surveys. During the bird use surveys, 91 single birds or groups totaling 250 individuals were observed flying. Of the large bird types observed, 54.2% were flying below the ZOR for potential collision with a turbine blade, 39.0% were within the ZOR, and 6.8% were observed flying above the ZOR for typical turbines that could be used in the Project. Of the small bird types observed, 96.9% were flying below the ZOR, 3.1% were within the ZOR, and none were above the ZOR. Bird types most often observed flying within the turbine zone of risk were waterbirds (100%), vultures (50%), and doves/pigeons (50%); however, this was based on only a few observations of groups or individuals. For species with at least 10 separate observations of flying birds, common raven was most often observed within the zone of risk. Based on the use (measure of abundance) of the site by each species and the flight characteristics observed for that species, common raven had the highest probability of turbine exposure, followed by great egret (Ardea alba), unidentified pigeon, and red-tailed hawk. No sensitive species were observed during surveys within the Ward subarea. The mean raptor use at each subarea was compared with 36 other wind-energy facilities that implemented similar protocols and had data for three or four seasons. The annual mean raptor use at these facilities ranged from 0.09 to 2.34 birds/20-min. survey (Figure 3). Mean raptor use at Ward (0.186 birds/20-min. survey) and CPC Proper (0.186) was low, ranking 33 rd and 34 th among the 36 other wind-energy facilities evaluated, and CPC East (0.038) was lower than all 36 sites (Figure 3). A regression analysis of raptor use and raptor collision mortality for 11 new-generation windenergy facilities where similar methods were used to obtain raptor use estimates showed a correlation (r 2 = 69.9%) between raptor use and raptor collision mortality. Using this regression to predict raptor collision mortality at the Project yields an estimated rate of less than 0.01 fatalities per MW per year for each of the three subareas (Figure 4). Based on species composition of the most common raptor fatalities at other western wind-energy facilities and species composition of raptors observed at the Project during the surveys, the majority of the fatalities of diurnal raptors will likely consist of red-tailed hawk. Nesting Raptor Surveys A survey for raptor nests was conducted throughout the spring and summer of The objective of the survey was to locate nests that may be subjected to disturbance and/or displacement effects from construction and/or operation of the project. The nest survey area included the primary project area and the area within an approximate 2-mile buffer of the project. One aerial raptor nest survey was conducted via helicopter on May 19, 2009 when Buteos (e.g., red-tailed hawk) eagles, falcons, and owls should be actively incubating eggs or brooding/attending young. Aerial survey methods involved a comprehensive search of suitable nesting areas and substrate (e.g., trees, rocky outcrops, cliffs, and other nest platforms such as Western EcoSystems Technology, Inc. 4 July 15, 2009

6 utility poles/towers and old wind turbines). Additional ground-based surveys were conducted throughout the spring and summer while observers were on site conducting other baseline studies. Ground-based surveys were conducted by walking or driving within the search area and looking for raptor nest structures within areas of suitable habitat. Additionally, data from fixedpoint bird use surveys were used to guide raptor nest survey locations if consistent observations of raptors indicated suspected nesting activity. GPS coordinates were recorded for all nests of raptors or other large bird species (e.g., ravens) and mapped on a GIS ArcView project utilizing USGS topographic maps (1:24000 scale) as the base. Locations of inactive nests were recorded as they may be occupied during subsequent years. During raptor nest surveys, six active raptor or raven nests, five inactive raptor or raven nests, and two nests of unknown status were identified (Figure 5). The active nests included four common raven nests, one red-tailed hawk nest, and one great-horned owl nest. Burrowing Owl Survey Burrowing owl surveys were conducted within the Alta-Oak Creek Wind-Energy Project from May 25 to July 11, Surveys were conducted throughout all proposed construction corridors located within areas of suitable habitat in each of the three subareas: CPC East, CPC Proper, and Ward. Survey methods were consistent with the Burrowing Owl Survey Protocol and Mitigation Guidelines prepared by California Burrowing Owl Consortium and recognized by the California Department of Fish and Game. Surveys were conducted by walking transects no greater than 30 m apart throughout construction corridors (Figure 5). All potential burrows and burrowing owl sign (e.g., pellets, feathers, whitewash) located during surveys were mapped. CPC East, Ward, and the majority of CPC Proper contain suitable burrowing owl habitat including existing burrows that could potentially be used by the owls, and burrowing owls have been observed within the CPC East subarea as recently as During the 2009 surveys, no burrowing owls were detected, and no burrows with evidence of current burrowing owl use were observed within the survey area. Two burrows with evidence of past use (i.e., old pellets and pellet fragments) were identified within the CPC East subarea (Figure 6); however, these burrows were partially collapsed or excavated and showed no signs of current use by burrowing owls. The data collected during these surveys suggests that the Alta-Oak Creek Mojave Wind-Energy Project is not within a high bird use area or major spring migration pathway. The study area does not appear to provide important stopover habitat for migrant songbirds based on fixed-point bird use surveys. Based on data collected during this study, raptor use of the Project is substantially lower than that observed at the Altamont Pass and Solano County projects in California, and is lower than the majority of other wind-energy facilities evaluated throughout the western and midwestern U.S. Additionally, the density of raptor nests is low relative to other regions in California such as Altamont Pass. The studies at this site suggest that avian mortality at the Project would likely be lower than that documented at several other wind-energy facilities located in the western U.S., where bird collision fatality has been relatively low. Although construction and operation of the wind-energy facility may displace some types of birds, because the Project will be sited in habitats that are common throughout the surrounding landscape, it is unlikely that displacement of birds would result in any population impacts. Overall, results of the Western EcoSystems Technology, Inc. 5 July 15, 2009

7 studies to date do not suggest that a wind development at the proposed site would have significant impacts to avian species. Literature Cited Western EcoSystems Technology, Inc. 6 July 15, 2009

8 Alta-Oak Creek Mojave Summary of Avian Baseline Surveys Figure 1. Fixed-point bird use survey stations at the Alta-Oak Creek Mojave Wind-Energy Project. Western EcoSystems Technology, Inc. 7 July 15, 2009

9 Alta-Oak Creek Mojave Summary of Avian Baseline Surveys Figure 2. Threatened or Endangered species located during avian use surveys at the Alta-Oak Creek Project. Western EcoSystems Technology, Inc. 8 July 15, 2009

10 Raptors Mean use (#birds/plot/20-min survey) Wind-Energy Facility Figure 3. Comparison of raptor use annually between the subareas of the Alta-Oak Creek Mojave Project and other US windenergy facilities. Data from the following sources: Ward, CPC Proper, and CPC East, CA This study. High Winds, CA Kerlinger et al Stateline Reference URS et al Maiden, WA Erickson et al. 2002b Diablo Winds, CA WEST 2006a Buffalo Ridge, MN Erickson et al. 2002b Hatchet Ridge, CA Young et al. 2007b Altamont Pass, CA Erickson et al. 2002b White Creek, WA NWC and WEST 2005a Biglow Canyon, OR WEST 2005c Elkhorn, OR WEST 2005a Foote Creek Rim, WY Erickson et al. 2002b Wild Horse, WA Erickson et al. 2003b Cotterel Mtn., ID Cooper et al Roosevelt, WA NWC and WEST 2004 Biglow Reference, OR WEST 2005c Swauk Ridge, WA Erickson et al. 2003a Leaning Juniper, OR NWC and WEST 2005b Simpson Ridge, WY Johnson et al. 2000b Golden Hills, OR Jeffrey et al Klondike, OR Johnson et al. 2002b Invenergy_Vantage, WA WEST 2007 Windy Flats, WA Johnson et al Stateline, WA/OR Erickson et al. 2002b North Valley, MT WEST 2006b Combine Hills, OR Young et al. 2003c Condon, OR Erickson et al. 2002b Tehachapi Pass, CA Erickson et al. 2002b Desert Claim, WA Young et al. 2003b Zintel Canyon, WA Erickson et al. 2002a Sunshine, AZ WEST and the CPRS 2006 Hopkin's Ridge, WA Young et al. 2003a Homestead, CA WEST et al Dry Lake, AZ Young et al. 2007c Reardon, WA WEST 2005b Nine Canyon, WA Erickson et al. 2001a San Gorgonio, CA Erickson et al. 2002b Western EcoSystems Technology, Inc. 9 July 15, 2009

11 Figure 4. Regression analysis comparing raptor use estimations versus estimated raptor mortality. Data from the following sources: Study and Location Raptor Use Source Raptor Mortality Source Buffalo Ridge, MN 0.64 Erickson et al. 2002b 0.02 Erickson et al. 2002b Combine Hills, OR 0.75 Young et al. 2003c 0.00 Young et al Diablo Winds, CA WEST 2006a 0.87 WEST 2006a Foote Creek Rim, WY 0.55 Erickson et al. 2002b 0.04 Erickson et al. 2002b High Winds, CA 2.34 Kerlinger et al Kerlinger et al Hopkins Ridge 0.70 Young et al. 2003a 0.14 Young et al. 2007a Klondike II, OR 0.50 Johnson NWC and WEST 2007 Klondike, OR 0.50 Johnson et al. 2002b 0.00 Johnson et al. 2003b Stateline, WA/OR 0.48 Erickson et al. 2002b 0.09 Erickson et al. 2002b Vansycle, OR 0.66 WCIA and WEST Erickson et al. 2002b Wild Horse, WA 0.29 Erickson et al. 2003b 0.09 Erickson et al Zintel, WA 0.43 Erickson et al. 2002a 0.05 Erickson et al. 2002b Western EcoSystems Technology, Inc. 10 July 15, 2009

12 Alta-Oak Creek Mojave Summary of Avian Baseline Surveys Figure 5. Raptor nests located at the Alta-Oak Creek Mojave Wind-Energy Project during spring and summer, Western EcoSystems Technology, Inc. 11 July 15, 2009

13 Alta-Oak Creek Mojave Summary of Avian Baseline Surveys Figure 6. Map of proposed construction corridors with inactive burrowing owl nests located during surveys conducted at the Alta-Oak Creek Mojave Project in spring and summer, Western EcoSystems Technology, Inc. 12 July 15, 2009