The California Condor on the Colorado Plateau

California condor. Photo by Neil Johnson, Los Angeles Zoo, courtesy of State of California.

The California Condor (Gymnogyps californianus) is one of the world's rarest and most imperiled vertebrates. It was federally listed as an endangered species on March 11, 1967. The condor is a member of the family Cathartidae, the New World vultures, a family of seven species, including the closely related Andean condor (Vultur gryphus) and the sympatric turkey vulture (Cathartes aura). California condors are among the largest flying birds in the world. Adults weigh approximately 10 kilograms (22 pounds) and have a wing span up to 2.9 meters (9 ½  feet).

California Condors  returned to the Colorado Plateau after at least a 72-year absence in December 1996 with the release of 6 birds at the Vermilion Cliffs on the Paria Plateau in northern Arizona. Of the 35 condors so far released in Arizona, 14 have fallen prey to eagles, coyotes, power lines, and, in one case, a man with a shotgun. Tragedy struck hard in the spring of 2000 when 5 mature birds died of lead poisoning, probably from eating carrion contaminated with shotgun pellets. All the Arizona condors were brought in for testing, and at this writing (summer of 2000) most are being treated for lead poisoning ranging from mild to life-threatening.

The fossil record of the genus Gymnogyps dates back about 100,000 years to the Middle Pleistocene epoch. The record reveals that the species once ranged over much of the southern United States. California condors nested in west Texas, Arizona, and New Mexico during the Late Pleistocene. Many fossils, eggshells, non-fossilized bones, and feathers have been found in caves within the Grand Canyon, indicating that it was an important historical nesting area. The Arizona specimens are between 9,580-22,110 years B.P., based on radiocarbon dating.

The disappearance of the condor and other large scavenging birds from these regions coincided with the extinction of the Pleistocene mammalian megafauna, their primary food source. By the time European man arrived in western North America, California condors occurred only in a narrow Pacific coastal strip from British Columbia, Canada, to Baja California Norte, Mexico. There is evidence indicating that condors returned to the southwest as early as the 1700s in response to the introduction of large herds of cattle, horses, and sheep that replaced the extinct Pleistocene megafauna as a source of carrion. The last sighting of a wild condor in Arizona was in Williams, south of the Grand Canyon, in 1924.

During the early 1900s condors were threatened by predator-poisoning campaigns, egg collecting, and museum collecting. More recently lead poisoning, collision with wires, and shooting have been the main causes of the population decline. By 1982 only 22 condors existed in the world. It was decided that the only way to prevent extinction of the species was to capture the last wild birds for captive breeding, with the intention of later reintroducing the offspring into the wild. On 19 April 1987, the last wild California condor was taken into captivity.

The recovery plan for the California Condor called for the maintenance of at least two non-captive populations and one captive population. These three populations must: (1) each number at least 150 individuals, (2) each contain at least 15 breeding pairs, and (3) be reproductively self-sustaining and have a positive rate of population growth. Following a widely publicized solicitation for suggestions for suitable condor release sites outside of California, the California Condor Recovery Team recommended in December 1991 that condor releases be conducted in northern Arizona. Because this area once supported California condors, and still provides a high level of remoteness, ridges and cliffs for soaring, and caves for nesting, the probability of a successful reintroduction was deemed very good.

In 1995 a release site was chosen near the edge of the Vermillion Cliffs on the southwestern corner of the Paria Plateau in northern Arizona just north of Grand Canyon. The Paria Plateau is characterized by relatively flat, undulating topography dominated by pinyon-juniper/blue grama grass communities and mixed shrub communities dominated by sagebrush on sandy upland soils. To the south and east of the Plateau lies the steep precipice of the Vermilion Cliffs, rising over 1,000 feet from the floor of House Rock Valley. Uplifting and differential erosion has created complex geologic structures and a diverse variety of habitats in a small geographic area. The cliffs are sharply dissected by canyons and arroyos and the lower slopes are littered with enormous boulders. Numerous springs emerge from the sides of the cliffs.

Whether the California Condor will survive in the wild is currently an open question. Ultimately it may be decided not only by the past land use history of the Colorado Plateau, but also by land-use decisions that we make today.

Resources:

Brodkorb, P. 1964. Catalogue of fossil birds. Part 2 (Anseriformes through Galliformes). Bulletin of the Florida State Museum. Biological Sciences 9: 195-335.

Collins, P. W., Snyder, N. F. R. and Emslie, S. D. 2000. Faunal remains in California Condor nest caves. Condor 102: 222-227.

Emslie, S. D. 1981. Prehistoric agricultural ecosystems: Avifauna from Pottery Mound, New Mexico. American Antiquity 46: 853-861.

Emslie, S. D. 1981. Birds and prehistoric agriculture: The New Mexican Pueblos. Human Ecology 9: 305-329.

Emslie, S. D. 1986. Canyon echoes of the condor. Natural History April, 1986: 10-14.

Emslie, S. D. 1987. Age and diet of fossil California condors in Grand Canyon, Arizona. Science 237: 768-770.

Emslie, S. D. 1988. Vertebrate paleontology and taphonomy of caves in Grand Canyon, Arizona. National Geographic Research 4: 128-142.

Emslie, S. D. and Heaton, T. H. 1987. The late Pleistocene avifauna of Crystal Ball Cave, Utah. Journal of the Arizona-Nevada Academy of Science 21: 53-60.

Ganey, J. L. and Balda, R. P. 1989. Distribution and habitat use of Mexican spotted owls in Arizona. Condor 91: 355-361.

Hunter, W. C., Ohmart, R. D. and Anderson, B. W. 1988. Use of exotic saltcedar (Tamarix chinensis) by birds in arid riparian systems. The Condor 90: 113-123.

Johnson, T. B. and Garrison, B. A. 1996. California condor reintroduction proposal for the Vermillion Cliffs, northern Arizona.Technical Report 86. Arizona Game and Fish, Nongame Endangered Wildlife Program, Phoenix, AZ, 102 pp.

Mead, J. I. and Phillips, A. M. I. 1981. The late Pleistocene and Holocene fauna of Vulture Cave, Grand Canyon, Arizona. Southwestern Naturalist 26: 257-288.

Mills, G. S., Dunning, J. B., Jr. and Bates, J. M. 1989. Effects of urbanization on breeding bird community structure in southwestern desert habitats. The Condor 91: 416-428.

Snyder, N. F. R., Ramey, R. R. and Sibley, F. C. 1986. Nest-site biology of the California condor. Condor 88: 228-241.

Snyder, N. F. R. and Snyder, H. A. 1989. Biology and conservation of the California condor. Current Ornithology 6: 175-267.

U.S. Fish and Wildlife Service 1996. California Condor Recovery Plan, Third Revision., Portland, OR, 62 pp.