Minecraft 1.7.2, Minecraft 1.7.4, Minecraft 14w02c, Minecraft 14w05b, Minecraft 14w20a, Minecraft 14w20b
While building my non-free range chicken highly automated chicken farm I noticed a massive swirling vortex of chickens forming underneath the dispenser. These chicken continuously jostle for position apparently trying to get to the same x/z coordinate as the "parent" chicken(s), even after the baby chick grows up. This condition persists until quitting and restarting, then they (at least the adults) resume normal chicken-y behavior.
This seems to happen when the chick cannot reach the parent. If I build a ramp up to the holding bin for the chickens laying eggs all the afflicted chickens make a bee line... or rather an extremely haphazard chicken line up to the bins to join their parents, again even the grown ups in the crowd who should have grown past such behaviors and settled into a life of clucking and pecking. I don't know what happens when they actually reach Mom and Dad. I had about 20 of them jump into the egg production bin and they just blended in with all the other chickens there...
Spawning a baby further away from the chicken bin seems to leave it parent-less and it lives a relatively lonely life clucking around the yard not wanting to be with anyone and certainly not obsessing over being directly below "Mom" and "Dad" (which, quite frankly, is not the best place to be standing in an automated chicken farm, lest you be constantly pelted with eggshell and falling baby chicks). He's the one off to the right in the screenshot, looking away from all the madness and mayhem. Doesn't he look sad and lonely?
Have not tested with pigs, cows or sheep as they don't lay eggs (that I know of) and can't think of how it would be possible to reproduce this behavior.
Placing a block near the vortex of death causes the chickens to begin a mad game of "king of the hill". What's interesting is while the king of the hill game is on, chicks dropping from the dispenser do not join them, they behave normally. If it's Y coordinate related, the ground is 7 blocks below the egg producing chickens, the "hill" is 6 and offset by about four blocks. Removing the block resumes the swirling vortex of death mode.
Holding seeds temporarily pauses their game and they all stare at me, rather creepily. Changing to something else resumes the game. If I breed two of the adults, they will "love" for a bit, drop a chick then resume the mad behavior but the chick will not be interested (probably for the same reason as the manually laid chicks being too far away?).