Taken from
http://www.cryptozoology.com/cryptids/thunderbird.php
"Perhaps the most controversial inclusion of the Thunderbird capable of lifting a human comes from 1977 in Lawndale, Illinois. It was here that on July 25, 1977 towards 9:00 pm a group of three boys were in the backyard. They saw two large birds coming, and as the birds came in closer they went after the boys. Two of the boys escaped, but the third, Marlon Lowe, did not. One of the birds clamped onto his shoulder with its claws and proceeded to lift the ten year old boy about two feet off the ground for a distance of at least 30 yards. With screams of distress calling adults outside and coupled with a series of blows by the 65-pound boy, the bird finally released him. The boy was relatively unharmed, with psychological damage instead of physical.
Although viewed by some as a tall tale, the descriptions given by the witnesses of these birds describe a large black bird, with a white ring on its neck and a wingspan of up to 10 feet, traits oddly reminiscent of the Andean condor (Vultur gryphus) which exhibits the same basic physical characteristics as that of the Lawndale bird. To this day, no one can explain away the incident from 1977 in any convincing manner, either the incident didn't happen or a large bird (of known or unknown status) attacked and carried a small boy one summer night to his and his family's terror.
The evidence thus far for the existence of a large undescribed predatory bird in North America is based on historical and modern anecdotal evidence with no physical evidence. There are however two tantalizing images of the Thunderbird, or at least of a large bird. The first was taken in the same year as Marlon Lowe's attack and in the same state. On July 30, 1977 John Huffer, an ex-marine and photographer, took a 100 foot roll of color film of two birds taking off from a tree in an inlet of Lake Shelbyville. The film concentrates on one of the birds only. Highly controversial, and thought by many to be of a turkey vulture, it sits as a little known film of a possible mystery animal. To date little, if any, evaluation of the birds in the film has been done. The Discovery Channel in their program "Into the Unknown" did give the film some mention, with a dismissal of a medium sized bird, probably a vulture.
The other possible photographic evidence is even more of a mystery, as it may not exist at all!! The image in question is the "Thunderbird Photograph" taken at the end of the nineteenth century in Texas. The image is said to depict six western clothed adult men, standing fingertip to fingertip in front of a barn where a large bird is nailed to the wall. Many have claimed to have seen or held this infamous image, including the late Ivan T. Sanderson who reportedly had acquired a photocopy of the image in 1966, the same year in which Sanderson gave the image, later lost, to a couple of men from Pennsylvania who were searching for the Thunderbird. The image has yet to surface, and may well not exist at all. The image was reported to have been published in 1886 in the Tombstone Arizona Epitaph, however this was somewhat dubiously reported in a 1963 article by Jack Pearl called "The Monster Bird That Carries Off Human Beings!" in Saga magazine. Searches of the Tombstone Epitaph have come up empty, aside from an article from April 26, 1890 of a 16 foot bird found in the desert by a couple of ranchers. So the mystery of the "Thunderbird Photo" is no closer to being solved then it was nearly 40 years ago during its first mention. "
