These gorgeous flaming birds have been classed as Birds of Prey. According to the database they're going to be tameable - unlike previous phoenix models. There are four standard colours, but by combining the different glow and base textures you can generate up to 16 colour variants!
Forsaken hunters automatically know how to tame undead creatures. Hunters of other races must learn the skill from a Simple Tome of Bone-Binding which is a rare drop from miscellaneous Elite NPCs throughout Maldraxxus and its associated dungeons: Plaguefall and the Theater of Pain.