How real is Tolkien's world?

[Alcuin]

There was a report in the 1970s from the plains of the United States of an enormous bird that picked up a 12- or 14-year old boy and began to lift him. His mother grabbed him, and the bird briefly lifted both of them before sinking under the weight and dropping them several feet from the ground. I have seen an interview of the mother and her son several times, and I recall reading the reports in newspapers and news magazines at the time. (I was roughly the same age as the boy, and the veracity of the reports was discussed over our kitchen table.)

The report recalled to some people American Indian stories of the thunderbird, a mythical bird of enormous size that could lift women and children, at least by some accounts. Many North American tribes have a tradition of this creature.

Hunters and farmers have very occasionally reported birds of enormous size in the United States, and there is from time to time video or photographic material to go with it.

But none of these reports – the boy and his mother, the thunderbird legends, or the incidental sightings of extraordinarily large birds – have ever been accepted by ornithologists, nor have any carcasses been recovered. The largest bird confirmed in North America is the California condor, a smaller cousin to the South American Andean condor. The California condor has a wingspan of about 3 meters and weighs about 10 kilograms. The Andean condor has a slightly larger wingspan and weighs as much as 25-30% more.

Eagles are known to steal sheep on several continents. An adult ewe can easily weight about 160 pounds (about 70 kilograms, or 11 stone).