When a chicken gets loaded in a chunk that has just been loaded, they will flap their wings a bit for seemingly no reason before stopping. I found this out by teleporting straight to a few chickens that were in unloaded chucks.

You can reproduce this by taking note of a chicken's coordinates, going far away from it, (probably about 200 blocks or something) and then teleporting straight back to the chicken. You should notice that the wings will flap for a brief period of time before stopping.