My Sr. thesis (2008) project at Western State College of Colorado focused on comparing sperm morphometry and natural ejaculate characteristics of the two species of Centrocercus grouse occurring in Colorado: Greater Sage-Grouse (Centrocercus nevadensis) and Gunnison Sage-Grouse (C. minimus). In spring 2008 we collected natural ejaculates from strutting male Greater Sage-grouse (Centrocercus urophasianus) in Moffat County, Colorado and from Gunnison Sage-grouse in Saguache County, Colorado. Natural ejaculates were collected by placing freeze-dried female greater sage-grouse in the copulatory position fitted with false cloacas on leks. We compared the ejaculate characteristics of sperm concentration, percent viable sperm, percent motile sperm, relative motility of sperm, percent structurally normal sperm, and the types and predominance of abnormal sperm in ejaculate samples. This study was intended as a preliminary investigation into the potential effects of inbreeding on Gunnison sage-grouse. With the exception of sperm concentration, we found few differences in ejaculate characteristics between the two species. However, we compared and found significant differences in the sperm morphometry of the two species. This study is the first to document natural ejaculate characteristics and sperm morphometry in a non-passerine bird species utilizing a polygnous lek mating system.