If you've played the new map pack on Ghosts, you might have come across a few egg hives like the ones in Extinction. Just like the Easter egg hunt you did with the Onslaught map pack, there are four new locations to find eggs in Devastation to unlock extra XP in Extinction Mayday and 20 Xbox gamer points.
Ruins: This hive is located near the C flag in Domination. There is a tower in the corner of the map and the egg is attached to the ceiling of it. It's easier to see it from the top of the stairs above the C flag over by the tunnel going toward the B flag.
Collision: If you spawn on the C flag, run to the right. Travel about half way across the map and look off the map at the bridge toward the C flag. The hive is located at the bottom right of the bridge.
Behemoth: This hive is located in a similar place to Collision. If you spawn at the C flag, run to the left hand side until you reach the small part of the pathway that juts out to the left. Turn 180 degrees and look down. The hive will be at the bottom of the excavation vehicle you're on.
Unearthed: This one is the easiest to find. Head inside the "dome" where the meteor is in the middle of the map. There is a broken part of the cylinder circling the meteor, closer to the A flag door. Look down and to the left and you should see it without an issue.
There you have it! Good luck finding the eggs. And don't forget to destroy the first hive in Extinction Mayday in order to unlock the achievement and egg-stra XP in the game mode.