Well, South Philly officially has red-tailed hawks. I confirmed this today while I was out walking the dog.
The first thing I noticed was an unfamiliar rasping songbird call. It sounded like the combination of "reeee, reeee" and running one's fingers along the teeth of a comb. I can ID a lot of birdcalls, but this one was new to me so it caught my attention. Then I realized there were NO OTHER birdcalls nearby. At all. That's VERY uncharacteristic for that intersection. The closest normal birdcalls I could hear seemed to be coming from at least half a block to a block away.
So I looked up and saw a hawk on a lightpole. I had to zoom the iPhone camera to get a recognizable image, so sorry about visual noise.
Shortly after I took the first images, I saw the bird that had been making the rasping call. An irate mockingbird started buzzing the hawk. I think they have a nest in one of the nearby trees, as it alternated between rasping in the trees and flying at the hawk.
When I turned my attention away from this interaction, and toward picking up after the dog, the hawk flew away. I didn't see what direction it took. But I will be on the alert from now on for absence of songbird calls (except for hostile calls), since that was my first clue that something was going on. If I notice that again, I'm going to start looking around to see if a hawk is around.