If you look at your map, I think I remember that there are 3 small caves/rooms in that cave system. When you enter the cave system, stay along the wall to your right. Go to the last cave/room (I think it's the third one). The yardbird is on the floor at the back of that little cave/room. The yardbird is very hard to see.
Boy, was this one hard to find. All the instructions made it sound like it was in the same cave where you torch the shelves where in fact it is not. It is in the cave directly across from there. When you first enter there are mobs wandering in the center with weapon racks on either side of the entrance. follow the wall around to the right and there is an alcove with shelves and a table. The yardbird is just left of the shevles. I hope this helps the next person looking for it.