Made a pass by the Ayer Mill Clock Tower this afternoon about an hour before sunset in search of the peregrine falcons.  The wind was light, out of the west with the temp about 17 degrees and a wind chill making it feel about 8 degrees.  At these temperature levels, the peregrines will shift over to the hot air vents on the south side of the Verizon Communications Tower on Canal St. between Hampshire and Franklin Streets. Sure enough, found the female perched on one of the upper vent ledges.  Just happened to catch the peregrine take off in flight into the fading late day sun, with less than an hour of sunlight left in the day.  It circled four times and landed on the NW corner of the roof and then flew off and landed again with a closer look!  The male arrived and perched on a nearby hot air vent ledge.

For those with an interest, four photos posted:

http://www.pbase.com/birdshots/image/164709980