As sightings of Rough-legged Hawks become fewer and further between, I have been reviewing this past winter’s images, and I notice a series of images of hawk hovering. Rough-legged Hawks are our only buteo that regularly hovers. In fact, the only other North American raptors that regularly hover are the Osprey and the collective kites. Hovering is defined as remain stationary in flight while continually flapping the wings. During hovering, the entire lift is generated by the action of the wings. Other raptors, including Red-tailed Hawks and Golden Eagles, can wind stall, which is remaining steady in the air by using an oncoming wind to compensate for the stall speed. Hovering requires a great deal of energy expenditure, and, even so, they have been known to hover for hours as they scan below them in search of a hapless prey. Their legs may be extended as they hover. For now, I will have to wait until next winter, when I will scan across some open field and see a silhouetted form flying without progress, a hovering Rough-legged Hawk.
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The best book on raptor flight that I have found is Hawks at a Distance by Jerry Liguori. You see my review of this great text at http://www.radleyice.com/2011/09/review-hawks-at-a-distance/