Speculation: I'd guess that you're removing arrows as skeleton drops. Making the too-many arrows problem from mob-traps a non-issue, and making chickens necessary to get a larger supply of feathers to make your own arrows, especially since you recently made bones more valuableFlowerChild wrote:...namely that chickens become rather useless later in the tech-tree, and secondly, what to do with the arrow drops that mob-traps produce...
If that's the case that's great, if not I'm looking forward to the surprise. :)