Avian mating systems are often monogamous, although polygamy in the form of both polyandry and polygyny are regularly employed by some species and opportunistically practiced by others. Among raptors, multiple species within the genus Buteo have been documented using either polyandrous or polygynous strategies. Here, we describe the first known cases of polygyny in Ridgway's Hawk (B. ridgwayi), a small forest hawk endemic to the island of Hispaniola. This raptor has been studied since the mid-1970s, and intensively during the last 20 yr. Ridgway's Hawks are generally considered to be monogamous; however, we report here observations of polygynous behavior in a recently established, wild population. We consider these polygynous breeding events opportunistic responses that display behavioral flexibility that may serve to benefit the conservation of this critically endangered raptor.