I've found some new images of various species of terror birds. Some of the more recently discovered species were truly enormous. The ones in my novel, THE FLOCK were the only North American version of terror bird yet discovered, Titanis walleri. These topped out at around 8 feet tall at the largest. But a newly identified species from South America was truly gigantic, topping out at over ten feet tall and having the largest known skull of any bird yet found in the fossil record. (That's the culprit in the sculpture here.)
As people like to say, Nature really did find a way. In this case, to bring back the theropod predators of the Cretaceous in a later age.
Today, the closest thing that we have to these amazing predators is the Secretary bird. Maybe Mother Nature will mold that creature anew into something resembling the tyrant beasts of 65 million years ago.