No you don't have to kill the bird, we had to go back to get this quest line, you have to place something (can't remember what) at the edge of the circle where Krolin spawns, the quest completes and you now have the quest line to follow. Sadly when you get to Garon's Mutation its broken and you can't go any further but that will take you to level 74.
I still have another Krolin quest thats not part of the chain at all, but in that one we would have to fight him and get a tail feather.