Saturday, October 5, 2013

Northern Harrier

Northern Harriers breed in the north half of North America and winter south to northern South America. Although they are common, I find them hard to photograph—perched birds usually fly before I get my camera focused, and taking pictures of flying birds is always a challenge. This photo was taken during a snowy spring in South Dakota.

Harriers are reognized by their long wings and tails; the gray males are smaller than the brown females. Both sexes show white rumps. They often fly near the ground over fields—their primary prey are voles (although I have also seen them take small birds, and harriers do take a wide variety of other prey). One reason for flying low is that, unlike other hawks, harriers rely on auditory, as well as visual, cues to find their prey,

Northern Harriers are intimately tied to their vole prey, so much so that Frances Hammerstrom wrote a book called “Harrier, Hawk of the Marshes: The Hawk That is Ruled by a Mouse.” When vole numbers are down, few harriers are seen; when vole populations expand, harriers become common. But the story does not stop there—males are often bigamous, especially when mouse populations are high. During abundant vole seasons, some males have up to five mates. The females incubate and brood their young, while the males provide most of the food for both their mates and young (Smith et al. 1011).

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