On a walk around Main Reservoir today (Kipling and Florida), Deb and I saw a large, entirely white-headed raptor, with dark moustachial stripes like a falcon today. We were on the Kipling side of the res, looking down at the tops of the light poles this bird was flying one-to-the-next, for a while. When perched, the tail looked narrow, was tan with thin dark barring. At first it seemed like a large falcon, too large for a Prairie, and the facial stripes lent to this thought, but further inspection showed obvious white scapulars, suggesting red-tail. We never got a look at the underside or breast, given our vantage, nor did it vocalize, so we settled on Red-tail based on the backpack straps, and a juvenile based on the tail and its erratic behavior of hopping impatiently from pole to pole every minute or so. Planning to go back tomorrow in hopes of better looks.