Commonly, the term mare is associated with an adult female horse. The term roan refers to a particular color pattern—a mixture of white and color (for example, white or gray sprinkles on a brown coat)—found in animals such as horses and dogs. A horse showing this coat color pattern is called a roan.
Somehow, these terms made it from the equine into crane terminology. Alex Shoumatoff notes (page 59 in ):
For some reason crane nomenclature is borrowed from horse terms. A mother crane is called a mare, the dads are roans. The terminology sounds like it was created out West.
Keywords: biology, ornithology, terminology, male, female.
References and more to explore
 Kachemak Crane Watch: SandHill Cranes, August 20, 2008 [cranewatch.org:8080/Cranewatch/news/sandhill-cranes].
 Alex Shoumatoff: Flight Club. Smithsonian March 2014, 44 (11), pp. 54-67.