If it isn't abundantly clear, if you go after this with too much DPS the dragon will NOT spawn. Others have commented the respawn time is six hours. I found this not to be true. It is exactly four hours, as of this posting.
It says in the description that a plains dragon spawns in place of this when its at 80% health but I saw both this and a plains dragon on track at the same time last night. Both were red to my 54 druid so I didnt venture near.
Poped right after I have killed The Silver Griffon (level 40 mob for unsolved jaggedpine quest).
I doubt they would be related ; instead, I think they are both on a "griffon&PH cycle", so to make him pop, I guess killing griffawns/fennes/fons might be a good idea ..