Chickens in nether

1. By "stronghold", do you mean "fortress"?
2. Is there a portal anywhere in the vicinity?
3. Have you found any eggs on the ground nearby?

1. Yes, sorry - meant fortress,
2. Portal is at 21 86 3; fortress is approx. -100 65 -50
3. Yes, found an egg.

Version 1.7.4 today: Also spotted chicken with egg in Nether more than 200 blocks from nearest portal.

Is this a improperly spawned baby zombie chicken jockey?

I know Zombies and zombie-pigmen sgare some code.

I know I'm quoting the Wiki (which I shouldn't as its incomplete) but it makes sense on what its says with:
"If the player goes far enough away, the baby zombie despawns but the chicken does not, leaving a regular chicken behind." so having a zombie pigman riding a chicken then despawning would make sense.

I have the same bug. Except I'm getting a lot more chickens since I've got a nether perimeter set-up but not complete. They spawn on the fortress and just around the nether. I have screenshots too if this needs more confirmed. They won't despawn right? So this could cause some problems.

I'm running on 1.7.4 on Mac OSX 10.6.8

Issues linked-

This should have been fixed due to the change that Chicken Jockeys despawn together now.
But I'm not sure, so I'm gonna keep it open.

I am still experiencing this on 14w03b (I can't edit the affected versions to add it), although much less rarely. I did a /kill @etype=Chicken to ensure all existing ones were dead, but after a few hops in and out of my nether hub, I started finding a few chickens (without a jockey on them) in the nether.

EDIT: I've noticed what might be a pattern, the chickens appear either in or very near to a portal when entering the nether. I have zero outdoor portals in my world (and no indoor chickens) so I know they aren't transferring that way. Not sure if that will help troubleshoot it, but thought I would pass it on.

They will despawn in time. They're a result of chicken jockeys that lost their rider.

Thanks, I had thought that they (as Galaxy_2Alex indicated) despawned at the same time as the rider.