Researchers followed up on the 2004 Energy Commission final report on bird mortality in the Altamont Pass Wind Resources Area (APWRA) by geo-referencing bird behavior data collected during 2002 and 2003, and performing spatial analysis on these data to test hypotheses that could not be tested previously. They related their 1,152 observations of raptors in flight to landscape attributes derived from a slope curvature analysis based on a digital elevation model of the landscape and ArcMap geoprocessing tools, and combined with wind directions recorded during the observation sessions. Red-tailed hawk and American kestrel flew over convex slope structures typical of ridges and hills disproportionately more often than over concave slope structures typical of valleys, ravines and basins. Red-?tailed hawk, American kestrel, and golden eagle flew over windward aspects of ridges disproportionately more often than over leeward aspects, and these results include the shifting of flights over aspects of the ridges (and hills) as the wind directions shifted. Locating new or existing wind turbines on the prevailing leeward aspects of ridges and hills should result in reduced encounter frequencies between flying raptors and wind turbines. Phase II of this project is ongoing, and will compare power output and wind turbine-caused bird impacts between the wind turbine owners' preferred wind farm design after repowering and a revised design based on our knowledge of bird behaviors and mortality patterns in the APWRA. The goal is to achieve an economically viable wind farm design that also minimizes bird mortality.