Reverse Sexual Dimorphism

http://www.uwgb.edu/biodiversity/projects/ptsauble/SSHphothigh.htm
The larger female and smaller male Sharp-shinned Hawks caught in their first fall. These size differences make it difficult to differentiate between female Sharp-shinned Hawks and male Cooper’s Hawks (a medium-sized Accipter). It’s important to look for physical differences such as head shape, tail shape, and tail length rather than relying on overall body size.