It was determined that the birds were not killed by the blades, but that the bats were. This study is on-going, apparently. In 1995 Cole and Associates did a survey of the research on bird deaths. So the industry had to see for itself the problem of birds being killed sometime long after the fact. Driving the necessity of new research and DOE funding are the possible violations of the Migratory Bird Treaty Act and the Endangered Species Act.
Many studies are in the works as of right now.
The Natural Renewable Energy Laboratory, a division of the DOE, is working with environmental groups, utilities, government agencies, university researchers, consumer advocates, utility regulators, government officials and the wind industry to address the effects of wind turbines on bird populations. Several meetings have been held to see where to proceed to address this issue. The meetings were co-sponsored by the DOE, the American Wind Energy Association, the Electric Power Research Institute, the National Audubon Society, the Union of Concerned Scientists and attended by interested public and private parties. Priority research projects were identified and are now under way. In a few years we may have a lot of answers to address the extent of the problem of bird mortality and how best to deal with it.