After the dinosaurs and other Mesozoic reptiles went extinct, they left massive voids in global ecosystems. Less than 5 million years later, niches once inhabited by carnivorous tyrannosaurs and herbivorous sauropods had been filled by birds and mammals.

In South America, the birds especially rose to prominence. As dinosaur descendants, the birds carried their ancestors’ torch through the Cenozoic era, acting as both predators and prey.

The most impressive of these Cenozoic birds were the predatory Phorusrhacids, commonly known as “terror birds”.

Titanis - Artwork by Dmitry Bogdanov
Titanis, a North American terror bird. Artwork by Dmitry Bogdanov.

Terror birds were flightless, carnivorous, and the largest apex predators in the ancient South American environment.

When the Isthmus of Panama formed 15 to 12 million years ago, they even made their way into North America and were the only South American predators known to migrate into North America during the Great American Interchange.

Phorusrhacos, a South American terror bird Artwork by Charles Robert Knight
Phorusrhacos, a South American terror bird. Artwork by Charles R. Knight.

Unfortunately, despite allowing the terror birds to spread into North America and terrorize the native North American fauna, the Isthmus of Panama ultimately led to their eventual undoing. Native North American predators such as wild dogs and cats were far more adaptable than the terror birds and invaded South America, which had previously been an isolated island continent much like modern Australia.

And, after 60 million years of terror, the Phorusrhacids finally died out 1.8 million years ago.

The video below clearly demonstrated the competition between Phorusrhacids and mammalian carnivores near the end of the terror birds’ reign. Here, the solitary terror birds are no match pack-hunting behavior of wolves.