These are the horror birds: tough, strong creatures who sliced through small mammals with the ease of the person who once used a pickax to pierce the skull of my insane uncle in a bar brawl (he survived, and no, I'm not even exaggerating).

You'd be excused if you tried to convince yourself that a pigeon's forebears were dinosaurs by gazing at one. After all, this monster evolved from some of the best killing machines evolution has ever produced, and it now sips gutter water and attacks the elderly in exchange for breadcrumbs. But before birds were begging for food in parks millions of years ago, they had already reached the top of the food chain. In actuality, they filled the voids left by their dangerous theropod ancestors like Velociraptor.

These are the horror birds: tough, strong creatures who sliced through small mammals with the ease of the person who once used a pickax to pierce the skull of my insane uncle in a bar brawl (he survived, and no, I'm not even exaggerating). The tallest of the 18 species, which can reach heights of 10 feet, chose not to use flight in favor of pursuing the beings that had just staged a party to bid farewell to the giant predatory dinosaurs. The unfortunate things had a hangover when they woke up, and the hangover was the terrifying bird.

The terror birds emerged as apex predators in isolation 60 million years ago in South America, which had not yet united with its northern counterpart. According to paleontologist Luis Chiappe, despite their success, their fossils are fragmentary and extremely rare. In 2007, he detailed the giant, oddly boxy noggin of the greatest terror bird ever: Kelenken, named after the dreadful bird spirit of Patagonia's indigenous Tehuelche people.

He declared, "It's the largest known skull for terror birds." In actuality, it's the biggest bird skull ever discovered. It is a massive, monstrous creature that is around 2.5 feet long and has a huge hook on the end of its beak that resembles an eagle.

Paleontologists believe that terror birds were not crumb-loving pigeons based on fossils like these, and not just because there was no bread in those days. Even while a skull cannot reveal the precise method of death, to Chiappe, this is unmistakably a carnivore's beak.

We all know that a cockatoo, a small parrot, can rip your finger off, the man remarked. Imagine the harm a bird like this could have caused with just one stroke from its enormous beak and skull. So that's definitely one pretty simple way to picture how these animals would have murdered their prey.

The fearsome birds resided in woods, where they were probably waiting in ambush on the numerous tiny mammals that arose in South America after the extinction of the dinosaurs. However, biomechanical tests have demonstrated that their skulls and beaks likely weren't robust enough to take on enormous animals. These were highly quick, swift predators, reaching speeds of maybe 30 mph, and they would have been more than capable of pursuing scampering creatures with their massively expanded legs. (This shouldn't surprise anyone who has seen how ostriches gallop, like huge 40 mph feather dusters having panic episodes, in a really frenzied and entertaining manner.)

Terror bird legs ended with talons, thus it's possible that the creatures shot their prey in the head with their beaks before standing on it and quickly shivving it to death. Or perhaps they shook and chomped on their prey until its spine broke.

For further conjecture, we may also investigate the living relatives of the terror birds, the seriemas. Even though these South American birds are only a few feet tall, they are skilled predators. They catch lizards, rodents, and other prey with their talons and smash them against rocks to break their bones.

Even the idea has been floated that the horror birds weren't actually terrifying. Instead, they were fervent vegetarians, or hunted birds. German researchers published the findings of a geochemical investigation of terror bird bones last year, concluding that the bones' calcium isotope compositions were more consistent with herbivores than carnivores.

But Chiappe rejects the idea that a creature with such a formidable build was anything other than a predator. He contends that the terror birds had extremely enormous heads compared to their bodies, much like modern eagles and very different from contemporary omnivorous terrestrial birds like emus, ostriches, and cassowaries.

"I personally think that you can come up with all these very rather innovative views, but I think that it makes a lot of sense that these animals were predators," the man stated. The same thing happened when someone proposed that T. rex was a scavenger. They undoubtedly consumed dead food, but it certainly caused death.

He continued, "Maybe [the terror birds'] bite force was not strong enough, or perhaps they were restricted to preying on particular animals, but that doesn't, in my opinion, make them a non-predatory bird."

Whatever their food and feeding habits, the terror bird empire began a steady fall starting around 4.5 million years ago, when the Central American isthmus developed, connecting two previously independent continents. All those species who had spent millions of years in seclusion were now mixing, schmoozing, and shaking hands - with their teeth.

While the apex predators of North America—bears and big cats—colonized South America, terror birds migrated up into what is now the southern United States. As a result, Chiappe explained, "they had to contend with new competition for the same resources, and that, coupled with possible climatic changes they may not have been able to handle and that may have affected their hunting strategies, probably drove them to extinction."

Because of this, no matter how dangerous a bird may have been, a cat has always managed to keep it under control. It was somewhat reminiscent of Sylvester and Tweety's never-ending conflict, only with more violence and fewer speech problems.