Thanks again to our friends at The Other McCain for the Rule Five links!
It turns out that a prehistoric monster bird roamed Ellesmere Island, in the high arctic, back in the Eocene. Excerpt:
It’s official: There really was a giant, flightless bird with a head the size of a horse’s wandering about in the winter twilight of the high Arctic some 53 million years ago.
The confirmation comes from a new study by researchers from the Chinese Academy of Sciences in Beijing and the University of Colorado Boulder that describes the first and only fossil evidence from the Arctic of a massive bird known as Gastornis. The evidence is a single fossil toe bone of the 6-foot tall, several-hundred-pound bird from Ellesmere Island above the Arctic Circle. The bone is nearly a dead ringer to fossil toe bones from the huge bird discovered in Wyoming and which date to roughly the same time.
The Gastornis (formerly Diatryma) fossil from Ellesmere Island has been discussed by paleontologists since it was collected in the 1970s and appears on a few lists of the prehistoric fauna there, said Professor Thomas Stidham of the Chinese Academy of Sciences in Beijing. But this is the first time the bone has been closely examined and described, he said. Gastornis fossils also have been found in Europe and Asia.
Gastornis was a monster indeed, a big bipedal critter with a head the size of a horse’s, bearing a big, heavy beak.

A Gastornis would have been a fearsome sight indeed. But should you have been frightened by the appearance of one of these big birds? Maybe not; they may well have used those big beaks for crushing tough plant foods. So, not such a terrifying sight.
Not such a fun hunt; at least not one bearing that touch of danger that makes hunting big apex predators exciting.

Not so much for their cousins the Phorusrhacids, who roamed the southern part of North America until a bit less than two million years ago. These fellas were nasty – a big hooked beak that they apparently used to hammer prey into submission. They were fast runners, too: Imagine an ostrich on steroids with the beak, talons and dietary habits of an eagle.
Had I a time machine, that’s a bird I’d like to hunt. They ranged up to nearly ten feet tall, but that’s not too big for my Thunder Speaker to take on; a .338 Win Mag should pack enough punch for one of these birds.
Still: One would have to shoot accurately and fast.
It’s too bad that their only surviving relatives present no such challenge. But that’s all the more reason to get some high-forehead types to build a working time machine.