Terror birds Thunderbirds or Phorusrhacidae, as they are variously called.
Were a species that lived in the Americas. There were many types of them. The largest of these species reached 3 metres high, during the period when a small amount reached N-America. Most were 1.5-2.5 metres high and lived in S-America. What killed them off was a the Central American land bridge formed by volcanoes linking South America with the North. This land bridge brought in kinds of Saber tooth Tigers which replaced them. What was amazing about these birds was that they were carnivores, unlike the ostrich style, Australian giant geese, and Madagascan elephant birds, called aepyrornis and NZ moas. They became the top carnivores in the continent till the tigers arrived. Top in terms of killing, not top in terms of anything else. They chased giant armadillos the size of cars, and probably all animals, like camels. They could catch armadillos, and probably the small moose or horse species of then. They could run at 30 mph, mabye even 60 mph, over short paces. It is felt some chased animals, and caught them, and that some were doing kung-fu on them, and eating the marrow in the bones. They weighed 2 people, and the some weighed more. The largest had a beak as large as a horses main. They lasted from 65 million to 2million years ago. They could have chased and killed people easilly.
Also a flying 8 metre wingspan, bird, that was 2 metres high died out 2 million years ago in Argentina. Look at http://www.lonympics.co.uk/
Other giant birds, included the moas, which were herbivores, and fed on vegetation in NZ. They died out in the 19thC, after Maori lifestyles had hunted them to small numbers, but then European colonisers diseases and dogs killed them off. Some Maori towns are still named after some of these 13 feet high, 2people weight animals. Others included the Madagascan elephant bird, which weighed people. It layed eggs a foot long, and was seen by Islamic traders then the French. Local legends called them shy creatures, it died out in the 17thC. With added to this a eagle in NZ that preyed on moas, and had a wingspan, of 3 metres. Also there were 3 metre high geese in Australia, till 30,000 years ago, eating who knows what, and slightly large ducks and geese on Hawaii, before the humans arrived. But nowhere near as the giant birds of these other tales in this paragraph. There were myths for instance mentioned in the story of Sinbad of giant birds, and many say this could have been influenced by the Madagascan birds. It has also been recently discovered that till maybe 1600, there was a Madagascan eagle that hunted lemurs, and this creature was the Stephanoaetus maheryi, Madagascar hawk-eagle. It was very big. It is felt that 2.5 Million years ago, raptors were able to feed on us humans, when we were young. evidence has been found in parts of Africa that even some surviving eagles of today could have done that, and marks have been found on bones that indicate that from past years,
Today the nearest comparison to this is the Sea-Eagle, of the Pacific. Which is a bird with a 10 feet wing span, which can be 4 feet high, some even 4 feet, and weighing a quarter of a person, Also ostriches which can at most reach 9 feet high, and a small bird in California that makes nests in trees 140 feet high. The great bustard can reach 4 feet high, and lives in Eurasia-African, and weighs a quarter a person. And the Andean condor weighs half that but can get as tall, as do some vultures. Look at http://www.lonympics.co.uk/
Some like to think there are still thunderbirds in South America, but that is unlikely. There are also many unsubstantiated sightings of large terror birds in North America. Just like in the Indian legends, Some have seen 6 feet high birds, they feel in the distance eating dogs. they feel were sea eagles.
There are tribes on the Washington state coast who have worshipped the Thunderbird, a bird in the mountains, that if people near causes tsunamis, or avalanches. This coastal tribe claimed that a large amount of very tall tree, stumps, on the British Columbia coast were caused by a fight between this bird and it's prey the killer whale. Actually modern scientists have decided it was probably caused by a tsunami, that also hit Japan, a couple of centuries ago. Today some people claim to see 6 feet high thunderbirds, in North America, like sea eagles, eating dogs, as they drive past, and some even higher. I suspect there could be 6 feet high sea eagles.
8 million years ago there were also buffalo sized giant rodents, walking around South America, I tell you if they had sent the local pest control people, there they would have said well get rid of theses, and then they would have seen the rodents.