From Blair A. in Gilbert, AZ (a co-worker and friend of the Avimor Bird Guy. We traded text messages while I was at the IBO with my family, so here is the dialog:
What's that name of the bird that darts around in the night skies in the Phoenix valley? They have an erratic flight pattern, almost like a bat, but they're birds.
Avimor Bird Guy: Lesser Nighthawk maybe. White wing patches?
Blair: They appear to be fairly sleek with long wings and I think a white stripe towards the end of the wings but it could be a patch. Hard to see at night. I've seen them most of my life and they seem to be most prevelant in the summer and fall. My son has been noticing them lately and wanted to know what they are. I'll lookup a pic of the lesser nighthawk.
Avimor Bird Guy: Lesser Nighthawk for sure then.
Blair: I looked them up. I think that's the one. Is it common to see several of them flying around in the same area at once? I assume the erratic flight pattern is due to them chasing insects in flight?
Avimor Bird Guy: Yep. You can occasionally see them roosting parallel on a branch or on the ground. Up in Idaho we have Common Nighthawks.
Blair: Thanks. I've always wondered what they were. My son and I have been seeing them flying around a certain farm field lately as we've been driving home from his football practices at about 7:45pm. I think I'll take him out there this weekend to watch them.