I think bears have quite efficient digestions, so they can probably utilize those birdseeds a lot better than us people.
Diva, our dachshund is that kind of a opportunist as well. If there's a bag of potato chips on the living room table, and you get up to go to the toilet, you will hear a rustling sound once you're behind the corner. If you come back and take a look, the dachshund will be back in the same spot in the couch. Then you go away again, and hear the sound, and sneak back behind the corner, and see her taking one potato chip out of the bag, and return to the couch. When she spots you, she stops chewing and looks very innocent. Sneaky little thing. But if she knows that she has no chance of getting something otherwise, she will lunge at things, for example if you were to drop one of the potato chips, she will inhale it withing half a second.