Watching (and hearing) the regular knocking of a cardinal against a window is painful at first. Naturally, the bird elicits sympathy--at first. With each attack against the unforgiving window pane, the observer cringes. The first time that the agressive cardinal wakes the sleeper from a very needed afternoon nap, the sleeper wakes with concern. After about two or three nap interuptions, the concern hardens to annoyance, and beyond that, thoughts of pellet guns surface.