Abstract
- This report presents the results of a radar and visual study of Marbled Murrelets conducted at the proposed Bear River Windpark (BRW), located in northern California. Radar observations were conducted for two days in June 2006 and two days in July 2006, at each of six sites. Radar sampling occurred during the morning activity period for Marbled Murrelets (i.e., from 75 min before sunrise to 75 min after sunrise).
- The primary goal of this study was to collect information on the number and flight paths of Marbled Murrelets flying in the vicinity of the BRW and then use those data to estimate an exposure index for Marbled Murrelets to the proposed wind energy facility.
- We observed ~0.3 landward targets/km/ morning in the BRW.
- There was some intersite variation in radar counts, but no obvious areas of high concentration or "bottlenecks" of murrelet use in the BRW.
- Our exposure indices suggest that 0.1-1.0 murrelets/morning would have passed within the airspace occupied by all proposed turbines at the BRW. Note that these exposure indices estimate how many times a murrelet(s) would be exposed to turbines, not the number of murrelets that would actually collide with turbines (because some unknown proportion of murrelets would detect and avoid turbines and some could pass through the blades without collision). Also, the exposure index calculates the number of exposure incidents, not the number of individual murrelets (i.e., the index takes into account that a single individual could be exposed to turbines multiple times).