Pixel transfer?
A good observation on your part, and it can't be ruled out, considering it was acquired with a personal video system and then probably degraded, digitized and compressed for transmission. For what it's worth, I have a very high-end video card and Hi-res screen, but if the input data is poor, my equipment can't improve it.
My analysis relied heavily on the 2Hz flicker, without that, I might have to go with the balloons too. Still, those sure do look like seagulls: the speed, altitude, the wide random spacing, the roughly linear formation and the flap frequency. Not to mention they like to fly home from the city dump around sunset.
Maybe Miami CSI can enhance it...