You learn this expression very fast, especially if you wanted to keep eating that sandwich.
We called this "regarding", overloading the word's meaning beyond the mere "to look at attentively; observe closely". If a chicken was looking at something with that intensity, it meant something, and we knew what it meant.
Check out the image here. Not the drinking hen, the one with her face in the camera.
If you ever see a chicken looking at you like that, make sure it's not within beak-range of anything important, such as your eyes. Guard your lunch well.