Birds are a family of animals that descended from the dinosaurs. They are found worldwide.
They are a clade of modern air-breathing, warm-blooded vertebrates. The ones that currently survive lack teeth, but possess a horny or bony beak, are covered in feathers and can fly. Yet birds are not related to pterosaurs or bats (mammals), and instead, they are dinosaurs - the only ones who had survived the K/T mass extinction.
Large, flightless Terror Birds like Phorusrhacos appeared in South America and eventually spread to North America after the two continents connected. They were the top predator in their ecosystems until being ousted by Smilodon.