Everything You Need to Know about FarmVille Mystery Eggs
A special tip: the more chickens you add to your coop, the more mystery eggs you'll be able to collect. The note in the game also says that the more variety of chickens you have in a Coop, the better quality your eggs will be. So, keep an eye on your Facebook feeds and collect as many mystery eggs as possible.
FarmVille Chicken Coops: Another Handy Tool for Power Farmers