Paperback in very good condition. This is an unabridged and corrected republication of the work originally published in 1953 as Research Report Number 4 of the National Audubon Society. Among the rarest of North American birds, the California condor hangs on to existence with remarkable tenacity. To better understand this bird and its ability to respond to human aid, the National Audubon Society and the University of California at Berkeley initiated the extensive field research that led to this 1953 study of its natural history. 31 photographs and 15 other illustrations.