GRE Reading Comprehension: JiJing 352-GRE阅读机经352篇 - W09KEA52867LM0S3K

Although the passenger pigeons, now extinct, were abundant in eighteenth- and nineteenth-century America, archaeological studies at twelfth-century Cahokian sites in the present day United States examined household food trash and found that traces of passenger pigeon were quite rare. Given that the sites were close to a huge passenger pigeon roost documented by John James Audubon in the nineteenth century and that Cahokians consumed almost every other animal protein source available, the archaeologists conducting the studies concluded the passenger pigeon population had once been very limited before increasing dramatically in post-Columbian America. Other archaeologists have criticized those conclusions on the grounds that passenger pigeon bones would not be likely to be preserved. But all the archaeological projects found plenty of bird bones and even tiny bones from fish.