Juveniles have a reddish patch on the breast. Sibley says this buffy wash on the breast fades within weeks, and calls this a "White-tailed Kite". I used to follow the usage of the Jasper Ridge bird card: "Black-shouldered Kite". See also the bird photography of Peter LaTourrette: <
http://www.birdphotography.com/species/wtki.html>;