Researchers studied flight responses of California condors to spatial and temporal variations in topography and vegetation to help understand the risk that obligate-soaring birds face from potential wind energy development. Tracking 24 condors with GPS over nearly 2 years, researchers found that birds flew at lower altitudes closer to the rotor-swept zone of wind turbines under a number of circumstances: over ridge lines and steep slopes, over forests and grasslands, in mornings and evenings, and during the winter months, when thermal updrafts were weakest. Although condors only occasionally flew at altitudes placing them in the rotor-swept zone of turbines, they regularly used classes of winds preferred by energy developers. Results suggest that collision risk to large soaring birds from turbines should be relatively lower over flatter, less rugged areas and in habitat used during daytime soaring.

Poessel, S.A., Brandt, J., Mendenhall, L., Braham, M.A., Lanzone, M.J., McGann, A.J., Katzner, T.E., 2018, Flight response to spatial and temporal correlates informs risk from wind turbines to the California Condor: The Condor, v. 120, p. 330-342, https://doi.org/10.1650/CONDOR-17-100.1.