He was curious how much he could get away with if it was a trap. You see him go for the quick score and when there’s no reaction he gets greedier. Then after downing the second one and still no trap he decides to grab one more before getting out of there.
Blue Jays are corvids, and they're smarter than dogs. A dog already in possession of a large piece of meat will drop it to pick up a smaller piece of meat. This jay is definitely selecting for size.