The discussion of how to tell adult female from juvenile Merlins has come up several times in the past few months. There is variation in juvenile and adult plumage and great variation and overlap in race. Often it is impossible to tell adult female from juvenile Prairie Merlin (and the same for black Merlin). However, typical adult female and juvenile Taiga Merlins can be told apart.

 Check out these typical birds, juvenile on the left, adult female center and right (right bird - photo by Pete Gustas, "click" to enlarge). The juvenile is pale with brown streaks and a brown head. The adult female is buffer underneath with broader, "blobby" streaks, and a slate-colored head. The topside is also slate-gray compared to the browner juvenile. Notice the retained juvenile inner secondaries and upperwing coverts on the topside, that are browner in color.