Terror Birds

When I was in high school I did a presention in AP Biology about "terror birds" - an extinct branch of the bird family that reigned in North America before the arrival of cats. as the name implies, terror birds were giant carnivorous birds. I remember being very captivated by the artistic renderings of these massive beasts feasting on deer. It was entertaining to envision myself fleeing from birds as large as myself.

I read a recent article indicating that the largest known fossils indicate a ten foot species. Seeing this skull next to a modern condor certainly puts this threatening animal into perspective.

If I would be intimidated by this modern bird...
...how would I far against one ten times as large?