Unusual Bird: White Throated Grackle

Sighted at a backyard birdfeeder with a large flock of Grackles. At first, I thought it was something stuck in its beak, but on closer inspection, it was clearly two white spots, one on each side of its neck under its beak.
From the grainy pics it just looks like a blip on the window but I also have a move where you can better see the bird moving with the two spots most visible. However, this app won’t allow me to upload the movie.