A birth animation is simply the animation that is created for when a character spawns into the game world. For most characters, this is something very simple but as Metal Maw is a big and powerful boss, the team at Carbine opted for something more epic and dramatic. For Metal Maw's birth animation, he flies up out of a hole in the ground and lands, preparing for the battle. The process is interesting and Carbine Studios' Senior Animator, Seth Kendall does a great job mapping it out so non-developers can understand what goes into these processes.
Check out the full blog entry at http://www.wildstar-online.com/ for another video and more information.