They were not mating for certain. Out of season and no raptors to my knowledge do it on wing. Mating when females stands on solid perch, sometimes rim of nest. Seen many times with local red-tails and red-shouldered.
Could somebody have been carrying a small bird and they were fighting over...
Turkey vulture, black vultures and red-tailed hawks outside fo breeding season. To my knowledge the only diurnal raptors that maintain territories outside breeding season in your and my area are red-shouldered hawks. Neither vulture species maintains territories at any time excepting around...