It was 65 million years ago that dinosaurs lived on Earth in what was commonly referred to as the Age of Reptiles or the Cretaceous Period. Flooding, freezing, and then acid rain killed the dinosaurs and many other animals on the planet, and this cataclysmic event marked the end of this time period and the beginning of another, the Cenozoic Era, which is sometimes referred to as the Age of Birds and Mammals. The smaller animals that survived the change of eras was able to sustain itself on the little life that was left on the planet, something that could not have been accomplished by larger animals who required a greater food source. It was during this time that a new giant animal came to existence, and it could be argued that the Cenozoic age could also be called the Age of Giant Birds (Alvarenga). While birds of unusual sizes existed on multiple continents, it is the birds of South America that spur the most interest, as they were carnivorous “Terror Birds.”
Birds the size of ostriches and larger roaming the world as predators is interesting in itself, but there are still a lot of questions in regard to these incredible animals. The predatory nature of the birds has been questioned around the world and only now thought to be true in South America. Their modes of killing are still in question, as the fossil record is not complete. Lastly, there aren’t anymore giant birds from the Cenozoic Era. Although there are good theories, there isn’t any proof as to what killed off these successful predators of the time.
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"The Giant Birds of the Cenozoic".
The Phorusrhucidae were large flightless birds that were the primary South American predators for millions of years. The 17 known species chased down their prey with long, powerful legs. They had small wings but enormous heads the size of horses’ heads. The smallest species was 80 centimeters, but the largest was 3 meters tall. As South America was largely filled with herbivores, the Phorusrhucidae could hunt and kill anything. They’d hunt down their prey with their speed and kill it with their beaks (Alvarenga).
Birds like the Kelenken had a skull that was 28 inches long. It was seven feet tall and weighed 400 pounds. The Andalgalornis could run 40 miles an hour, which would make it the fastest known biped ever in existence (A Central Coast Paleontologist). While these birds would have been no match in size or stealth for the flying pterosaurs of the Cretaceous Period, they would provoke deathly fear in any present day human (Vermeij).
The end of “terror birds” happened approximately 2.5 million years ago (Wilson). It is debatable why it happened. Some speculate that they encountered predators when Central America connected North America and South America. This would seem a very likely scenario except for the fact that the large carnivorous bird Titanis lived in the area that would now be the Southeast portion of the United States for 3.1 million years (A Central Paleontologist). It seems that the “Terror Birds” were surviving successfully amongst the competition.
It is also not known exactly how these predatory birds killed their prey. It is assumed that the Phorusrhucidae chased down their prey due to their strong ostrich-like legs. It would have then used its heavy head and beak to eviscerate or peck the prey to death. Some scientists believe the birds may have stomped the prey to death or at least until it was immobilized, then tearing its flesh away from its body. It is unclear exactly how these birds obtained their food. This is also true of the giant herbivore birds around the world during this time.
Mystery and speculation about the end of the giant birds of the Cenozoic period are not the only unknowns on this subject. It was first thought that the giant birds of Australia were also predatory. The Gastornis was also called “The Horse Eater.” It was a two-meter tall bird that hunted down the horses of that period. It had a beak that was heavy and could crush the horse’s spine. However, this beak turned out to be a limiting factor that would prevent mobility. The bird’s eyes rested on the side of its face, much like other herbivores. The beak and the claws were blunt. The “Demon Ducks” of Australia also had eyes on the sides of their heads. Many of the birds had stomach stones meant for grinding leaves (Woodruff). It turns out that they were all herbivores except in South America. While “Terror Birds” reigning the Earth makes for a horrific tale, it is believed that the only predatory giant birds were the South American Phorusrhucidae.
In 2014, a paleontologist out of California, discovered a large prehistoric bird that had been stored in a museum for 30 years waiting for further identification. It is the largest flying bird ever identified with a wingspan of 20 to 24 feet. The pseudoteeth of this animal’s beak was made from protrusions on its jaw, but it was a meat eater, likely eating fish and waterfowl. This discovery may not add to the category of “Terror Birds,” although it would be terrifying to see the bird flying anywhere nearby. Its discovery does highlight how much there still is to learn about the giant birds of the Cenozoic. The mysteries and unknowns are too great to stop investigating at this point.
