Anecdote here. I keep 8 chickens as pets and for an egg supply. Each morning, I feed them a quantity of mixed-grains fowl feed. This is strewn on the ground, usually in a rough line or a few spots. They then proceed to peck up this feed. I started feeding them enough so that there is some left after they had finished. I then adjusted the quantity down so that there is no wastage - discouraging rodents and other birds from the area. (Chickens are left for the rest of the day to forage free range.)
In the beginning of a feeding session, while there is plentiful, "sharing" gets along nicely. Everyone pecks away in his/her own position. Smaller chicks will be called with a specific sound (mostly be the mother, but others may do it too), shown a piece of grain in the beak of the caller, which is then deposited near the chick for it to eat. The rooster will also use this sound to "call" the hens to come and eat. All nice and commie altruistic, one gets tears.
About halfway through the feeding session, when the food has been diminished by about half, things get interesting. Those higher up in the pecking order (natural fowl social hierarchy) chase away those lower down, to get to their food. No matter that the "higher-up" still had some left where she was pecking. No matter that there should be (just) enough for everyone. No matter that there is a whole day left to forage more. Looks to me quite like the nasty monopolizing side of capitalism from where I stand.
Please people, don't come preach about animal behavior and present that as the absolute and static alpha and omega. Circumstances change, even in a single feeding session.