Out of the 50ish dragons I've seen, at least half have done this. It svcks, but, as far as I can tell, is unavoidable.
There are also some dragons that just fly, never landing, never attacking anything. You'll see them on your compass as markers shaped like a front facing dragon head.
Wow, that's not what that is at all. Those icons are spots on the map where there's guaranteed to be a dragon--usually you're sent there from the Jarl of some nearby hold to slay it.