heres a few links i found...sorry its not really any "new" info but here it is anyways
Giant Bird in New Guinea from 1875 sighting
The natives state that it can fly away with a dugong, a kangaroo, or a large turtle. Mr. Smithurst states he saw and shot at a specimen of this
wonderful animal, and that "the noise caused by the flapping of its wings resembled the sound of a locomotive pulling a long train very slowly." He
states that "it appeared to be about sixteen or eighteen feet across the wings as it flew, the body dark brown, the breast white, neck long, and beak
long and straight."

here is a link about the native American legends of the Thunderbird...
The Giant Bird
There was the sound of a mighty wind and a dark shadow crossed over the land. The Bird of Thunder dropped lower over the edge of the herd and a young
calf was lifted into the air. Soon other shadows dropped near the earth and more of the young calves were taken. Lightning streaked across the sky and
the voice of Old Man Thunder spoke with a vengeance. The Mighty Birds that brought the storm disappeared in the distance as Mother Earth opened her
arms to receive the rain. The herd returned to their grazing now that the danger was past. Again the Mighty Thunderbird had stolen from the herd and
loosed another storm upon the land. Everything was as it should be, the herd had grown too large and Mother Earth had needed the rain.

heres is an article about the most recent sighting...from 2002
Mystery giant bird spotted in Alaska
A bird the size of a small airplane has been spotted flying over south-west Alaska, puzzling scientists, the Anchorage Daily News reported this
week.

[Edited on 6-10-2003 by Creepy]