by Nezark123 » Sat Jun 29, 2013 11:55 am
Once every so often Zerg kills 1/3 of all mobs in each chunk so as to allow passive mobs to spawn naturally again, otherwise we hit the spawn limit on the world, and no new players can start their own animal farms.
Typically though, as far as I've noticed, that wouldn't wipe out a chicken farm entirely. It's possible that was a contributing factor, but not the main reason.
I'd venture to say that most of your chickens suffocated to death if they were in a place where the chunk is often loaded. With all of the lag recently, the chickens push each other into walls, and instead of popping back out, they actually get killed and drop their items. Most likely a combination of this and the first thing is what killed your chickens.