We examined bird and bat mortality at a new 89-turbine windfarm constructed in an environmentally sensitive area in north-central Iowa. The windfarm became operational in November 2001. It is located in cropland between three Wildlife Management Areas (WMA's) with historically high bird use. In the past, migrant and resident waterfowl, shorebirds, raptors, and songbirds moved between the WMA's through the area now occupied by the windfarm. Studies of bird collision mortality in California and elsewhere raised concerns about the possibility of mortalities in this area. From April 15, 2003 and December 15, 2003 we searched for dead animals under 26 randomly selected turbines. Six 76.2 m by 3.0 m transects were maintained as bare ground under each of these turbines. Access roads and construction pads under turbines were also searched. We found two birds (a yellow-throated vireo and a tree swallow) and 31 bats (hoary, red, little brown, big brown and silver-haired bats). Spring and summer search efficiency and scavenge rates were evaluated. During observer efficiency trials, observers found 77% of bird carcasses. In spring and summer and fall scavenging trials, scavengers removed 7%, 12% and 7% of carcasses respectively, within the duration of observer search cycles (i.e., 2 days). Point counts were conducted to compare bird activity in fields with and without turbines. We monitored waterfowl activity and behavior in the fall. 1.2 million total goose-use days and 194,029 total duck-use days were recorded in the WMA’s, from September 15 to December 25, 2003. Canada goose foraging behavior was monitored for a total of 270 flocks, from September 27 to December 1, 2003. Bat detectors were used to compare bat activity at turbine versus adjacent non-turbine sites. No significant differences were found between relative bird and bat activity at turbine, turbine with transect and non-turbine sites. Results presented are preliminary. The study will continue until December 2004. While we have yet to evaluate the significance of the mortality data, proper siting of these facilities remains a priority.
Avian mortality associated with the Top of Iowa Wind Farm: Progress Report, Calendar Year 2003
Koford, R.; Jain, A.; Zenner, G.; Hancock, A. (2004). Avian mortality associated with the Top of Iowa Wind Farm: Progress Report, Calendar Year 2003. pp 1-9.