For comparing impacts of bird and bat collisions with wind turbines, investigators estimate fatalities/megawatt (MW) of rated capacity/year, based on periodic carcass searches and trials used to estimate carcasses not found due to scavenger removal and searcher error. However, scavenger trials typically place ≥10 carcasses at once within small areas already supplying scavengers with carcasses deposited by wind turbines, so scavengers may be unable to process and remove all placed carcasses. To avoid scavenger swamping, which might bias fatality estimates low, we placed only 1–5 bird carcasses at a time amongst 52 wind turbines in our 249.7‐ha study area, each carcass monitored by a motion‐activated camera. Scavengers removed 50 of 63 carcasses, averaging 4.45 days to the first scavenging event. By 15 days, which corresponded with most of our search intervals, scavengers removed 0% and 67% of large‐bodied raptors placed in winter and summer, respectively, and 15% and 71% of small birds placed in winter and summer, respectively. By 15 days, scavengers removed 42% of large raptors as compared to 15% removed in conventional trials, and scavengers removed 62% of small birds as compared to 52% removed in conventional trials. Based on our methodology, we estimated mean annual fatalities caused by 21.9 MW of wind turbines in Vasco Caves Regional Preserve (within Altamont Pass Wind Resource Area, California, USA) were 13 red‐tailed hawks (Buteo jamaicensis), 12 barn owls (Tyto alba), 18 burrowing owls (Athene cunicularia), 48 total raptors, and 99 total birds. Compared to fatality rates estimated from conventional scavenger trials, our estimates were nearly 3 times higher for red‐tailed hawk and barn owl, 68% higher for all raptors, and 67% higher for all birds. We also found that deaths/gigawatt‐hour of power generation declined quickly with increasing capacity factor among wind turbines, indicating collision hazard increased with greater intermittency in turbine operations. Fatality monitoring at wind turbines might improve by using scavenger removal trials free of scavenger swamping and by relating fatality rates to power output data in addition to rated capacity (i.e., turbine size). The resulting greater precision in mortality estimates will assist wildlife managers to assess wind farm impacts and to more accurately measure the effects of mitigation measures implemented to lessen those impacts.
The Alameda whipsnake (Masticophis lateralis euryxanthus) is a federally and State threatened subspecies of the California whipsnake (M. lateralis) and is restricted to a specific geographic range (Jennings 1983, USFWS 1997, USFWS 2002, Stebbins and McGinnis 2012. Until recently, the subspecies was believed to occur in Alameda and Contra Costa Counties, and in small portions of northwest San Joaquin County and northern Santa Clara County. Recent work suggests that the range of the subspecies may include eastern Santa Clara County and northern San Benito County, making the subspecies active in a wider area than previously believed (Richmond et al. 2016). Within its accepted range, the Alameda whipsnake has been the subject of study for nearly four decades, yet there remains a paucity of published work on this subspecies. After its initial description (Riemer 1954), Hammerson (1978, 1979 was the first to study the subspecies, and described its thermal ecology and reproduction; Larsen et al. (1991) and Shafer and Hein (2005) reported on the snake's feeding ecology with little detail about its general natural history; and Swaim and McGinnis (1992), Swaim (1994), Alvarez et al. (2005), Alvarez (2006 looked at the subspecies' use of habitat, with conflicting conclusions. These conflicts included a disagreement on the types of habitats, and slope aspects used. Currently, the natural history of the Alameda whipsnake remains mostly conjecture and assumption, with inferences made from work by Swaim (1994) or stemming largely from grey literature (i.e., unpublished technical reports). The draft recovery plan for the Alameda whipsnake, which summarizes the natural history, also uses limited published literature related to the Alameda whipsnake's biology. Here we examine and analyze a large data set on Alameda whipsnake activity and add to the published literature by reporting on its annual activity period.
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