Discovering that one California condor egg embryo has died and the other is in jeopardy, biologists have removed the eggs from a nest in a remote area of Los Padres National Forest in Santa Barbara County and replaced them with a ceramic "dummy egg" which the attendant female condor has accepted and continues to incubate.
Biologists from U.S. Fish and Wildlife Service (Service), Zoological Society of San Diego, and Los Angeles Zoo removed the eggs June 1, 2001, after it became clear that the condors were switching between the two eggs as they attempted to incubate them.
"There was no way that both eggs could still be viable when exposed to widely shifting temperature regimes and not being consistently incubated through the night," said Mike Clark, condor keeper and captive propagation specialist with the Los Angeles Zoo.
When Greg Austin, supervisor of the Services field monitoring program, entered the nest to collect the eggs, he realized by its strong smell and light weight that one egg was dead. "If by some miracle the other egg was to successfully hatch, the chick would probably not be able to survive in the wild," said Clark.
One of the eggs was incubated more consistently and the developing embryo was still alive. However, it showed signs of distress and abnormal development. Hoping to save this egg, Austin transported the egg to the Los Angeles Zoo for veterinarian care.
By placing a dummy egg in the nest, the parents should continue the nesting cycle. If they do, in about two weeks the dummy egg will be replaced by a condor egg which was laid in captivity at the Los Angeles Zoo. By receiving this egg just before it is ready to hatch, the wild birds will have a good chance to raise a chick in the wild.
"There are really two objectives in this effort to switch eggs. First, is to provide the wild birds the most experience possible in proceeding through the nesting cycle," said Austin. "Then, condors will take several breeding attempts to learn all the appropriate behaviors to successfully raise a chick to independence. Assisting the birds now will greatly enhance the possibility that they can successfully raise a chick next year. The second objective is to see a chick raised in a truly wild setting."
"There is no guarantee that this nest manipulation will be entirely successful," said Bruce Palmer, condor program coordinator for the Service. "However, it is central to the condor reintroduction effort that all efforts are made to give the birds every chance possible to raise a chick in the wild."
California condors lay a single egg, but in this case it appears that two females with a single male each laid their egg in the same nest cave. This is only the second nesting attempt by condors in the wild since 1982.
"We have never seen two females lay eggs in the same nest before, but then there has never been a situation like this either, when birds are reaching sexual maturity and there may not be enough mature partners,"
said Dr. Mike Wallace of the Zoological Society of San Diego and team leader for the California Condor Recovery Team.
In 1987, the last of 27 California condors were removed from the wild and brought into the captive breeding program. Reintroductions to the wild of juvenile captive breed condors began in 1992. Condors do not reach maturity until they are six or seven years old. This is the first year that reintroduced condors laid eggs in the wild. Currently, there are 34 condors in the wild in two areas in California, and 23 free-flying condors in the Grand Canyon area in Arizona. On March 25, 2001, the first egg laid by reintroduced condors was discovered in the Grand Canyon by biologists working for The Peregrine Fund, which manages the release program there. That egg was broken by the condors and the nesting attempt failed. There are 115 California condors being held in captivity.
Condors are scavenger birds that soared over the Southern California mountains and other areas since prehistoric times but their numbers plummeted in the 20th century. The causes of their decline are not completely known but lead poisoning is believed to be among the factors. Condors were listed as an endangered species in 1967, under a law that predated the existing Endangered Species Act. In 1982, the condor population reached its lowest level of 22, prompting Service biologists to start collecting condor chicks and eggs for a captive breeding program. By late 1984, only 15 condors remained in the wild and six of them died within a short period, several from lead poisoning. Lead poisoning occurs after scavenging birds such as condors, turkey vultures, golden eagles and bald eagles eat the meat of dead animals that contain lead fragments from bullets.
The goal of the California Condor Recovery Plan is to establish two geographically separate populations, one in California and the other in Arizona, each with 150 birds and at least 15 breeding pairs.
