Made a late afternoon pass by the Ayer Mill Clock Tower for a brief look at the peregrine falcons.  While scanning for the peregrines, noticed hundreds of American crows streaming into the area west of the New Balance building complex and preparing for their overnight winter roost.  In the midst of the crow chaos, noticed a single peregrine buzzing a few of the crows.  The peregrine landed on a number of lower than normal rooftop perch locations, perhaps to take a run at some of the crows.  As it perched atop the roof of B&D Advanced Warehousing Corp. building in fading sunlight.  As it moved around just a bit while perched, the bi-colored alpha-numeric leg bands were exposed.  It was the male with the black over green 6/4 left leg band!