Female dragons take much longer to mature than their male counterparts. They too undergo a metamorphosis of sorts at adulthood; But while males lose the use of their forepaws, females actually grow a third set of limbs specifically to serve as wings.
Young females travel great distances looking for a suitable nesting site. Because of their nomadic habits, these are the dragons most frequently encountered by man.
Dragons are immature females, the precursors to High Dragons. Always be wary, for they are strong opponents, capable of breathing fire and catching opponents beneath their talons. In the courtyard of Fort Drakon (Final battle), you will encounter a Dragon Thrall, it is basically the same, but will fight alongside the Darkspawn. The Thrall is probably a dragon minion of the Archdemon. During the ritual to become a Reaver, Kolgrim gives The Warden Wyvern blood to drink suggesting dragons are called by different names, there is another species of dragon, or that there is another step in the growth cycle of male/female dragons.