"Great photos, capturing the regal elegance and essence of winter red-tails. And you were correct on every point, especially about the birds' contentedness in the cold weather. Unless it's way below zero (F) for an extended time, several days or longer, these big hawks are entirely comfortable in winter weather. The fluffed-up feathers act like a thick down coat, keeping the hawks' body cores nice and toasty. They are masters of all they survey at this time of the year. Few other wild animals can live so comfortably in winter. Experienced haggard red-tails need worry for nothing.
Now this pair has surely stayed in the area for the winter. They did not migrate to the South. They were content to hang around, albeit not as closely to the nest site as in the breeding season. But now, they've detected that the day length, the photoperiod, is no longer declining. For them, the seasons are changing, prompting closer attention to the nest area.
No eggs will be laid until sometime in March. This is only the second year for the pair (at least at this site), so they aren't likely to be early. I wouldn't expect any eggs until mid-March, perhaps not even until the third or fourth week.