Details in the checklist
Another possibility is an imitation of a Sharpie by a Blue Jay. Merlin Song ID returned Blue Jay alone as a possibility, while BirdNET prioritized Sharpie (probability 0.37), followed by Red-shoulder (p = 0.09), followed by Jay (p = 0.08).
All About Birds mentions only Red-shoulders being imitated by Jay's.
Sharpies are currently migrating along the local ridges incl South Mtn very near the checklist location.