Originally Posted by Sangahyando
AFAIK there aren't really any birds in North America bigger than pelicans, though. In fact, pelicans are among the largest extant birds capable of flight. The bird might've appeared larger than usual because usually one doesn't get that close to them (also, sudden encounters can have that effect, in my experience).
The behaviour still fits a gull best (they are the only seabirds I know of that routinely pirate food from humans, and not just other seabirds), perhaps "just" a young American Herring Gull
Now I wonder what kind of bird would freaked people out about a Jersey devil, its dark lighting, seems authentic photo, but what could it be with such poor lighting? I've seen some pretty large gray bats around here but none that look like that! Could it be a bird, or kite? I would think the shape more for bat wings, but eyewitnesses say it look to them like a vulture.