Northern Harrier (Circus cyaneus) is an unusual raptor in that it exhibits a marked sexual dimorphy (male is gray, white and black and the female seen here is brown). In addition its proclivity toward polygyny (polygamy) is unusual. Both males and females are readily identified by their long tail and wings, white upper rump and by their behavior of glide-flying very close to the ground while hunting. It uses both site and sound to locate its prey and its owl-like facial parabolic disc helps to amplify and focus the source of sound. The Northern Harrier winters throughout coniferous regions of southern Canada and the US and into Central America and the Caribbean Islands. In their winter grounds, Northern Harriers generally roost communally on the ground. This harrier is commonly seen in California grasslands and fresh and saltwater marshes from September to April and some remain resident in the California central valley throughout the summer. It breeds primarily in north Alaska and Canada - preferring treeless habitats such as the tundra. Once on their breeding grounds, pairs form. Male Norther Harriers seek to attract females by their elaborate “sky-dancing display” where he may fly 100-300 meters high and cover up to a kilometer - flying and tumbling. He descends to a “suggested” nest site and if he is successful, the female follows. Some males are highly vigorous sky-dancers and these individuals may attract many females; The male may mate with as many as 5 females in his territory but most generally mate with only 1-2 females. Both the male and female chooses the site for the nest and begins its construction. The female lays 4-6 eggs and incubates these for 30-32 days during which time the male delivers food to his mate(s). Once the chicks hatch, the male continues to bring food to the female(s) and hatchlings and the female frequently leaves the nest and obtains food from the male via aerial transfers. The juveniles take their first flight from the nest within 4-5 weeks of hatching. Northern Harrier pairs produces only one brood a year. Northern Harriers eat small mammals such as voles, birds, amphibians and reptiles. Their presence overhead cause enormous alarms in colonies of Burrowing Owls. Their predators include other raptors and coyotes. In California female Northern Harriers often evict from their territories raptors that are bigger than themselves, but never raptors that are smaller than they are.