He photographed and drew detailed pictures of the wild whooping crane. He studied and documented the nesting habits of the whooping crane. It serves as a wintering ground for the endangered whooping crane. Bobcats are considered the major predatory threat to the endangered whooping crane. It is the only natural nesting habitat for the endangered whooping crane. Cheyenne Bottoms is critical habitat for many endangered species, including the whooping crane. It also includes the only known nesting site of the whooping crane. All three other birds are at least 30% smaller than the whooping crane. Wood Buffalo Park contains the only natural nesting habitat for the endangered whooping crane. Known as Whooping Crane Summer Range, it is classified as a Ramsar site. He began studying the whooping crane at the Aransas Refuge in Texas. The whooping crane was declared endangered in 1967. Whooping crane survival depends on additional, separated populations. The American white pelican and whooping crane also have longer bodies than the condor. Included in this list are the peregrine falcon, endangered whooping crane, and threatened bald eagle.