Strange Flock-fellows

Mike and Barbara across the street from me have a cat. The cat snagged a fledgling grackle that apparently didn't successfully fledge. Such is life. However, the grackles were not pleased. A family group of about 8 to 12 harassed that cat anytime it was outside and for days, (at least 3) after the incident. They made noise and surrounded the cat, dive bombing it from behind.

Oddly, though, a lone male Cardinal seemed to be with the grackles. I thought this odd, but Mike and Barbara both swear up and down that every time the flock harassed the cat, the Cardinal was there with the grackles, looking on, but never taking part. A couple of days ago, what I assumed was Mike and Barbara's flock of grackles, flew as a group from my yard to theirs. Moments later I heard the chip, chip sound of a Cardinal and sure enough, there was a male Cardinal with the flock.