Endangered condors lay first eggs in wild

California condors are again mating in the wild. There are only 59 members of this species outside of zoos. All captive-bred, they were released into their former habitat over the past 6 years through a program managed by the U.S. Fish and Wildlife Service. Last week, the agency announced that one of its biologists has spied a trio of the wild condors tending a pair of eggs.

Dad considers which of the real eggs to incubate. Brooks/USFWS/Nikon

Greg Austin last month spotted two eggs in the same dark overhang on the face of a remote Southern California cliff. Because each female produces a single egg, the presence of a pair in the cliffside hollow suggests that the two females share the single male as their mate. That’s surprising since the 25-pound condors ordinarily form monogamous couples for life. Both mother and father contribute to the intensive, nearly 2-year incubation and rearing of each chick.

Apparently, the mating triangle has confused the birds.

Scientists monitoring the parents from 150 yards away noted that often only one bird was on hand to guard the eggs. The lone sentry covered one egg for a time, then it scooted over to warm the other. Unfortunately, the eggs need more than episodic incubation.

Suspecting that the parents’ divided loyalties were compromising the survival of both fetuses, scientists moved in late last week and examined the eggs against a strong light. One fetus was dead. “The other was viable but had developmental problems,” reports John Brooks, a spokesperson for the agency’s Hopper Mountain Complex outside Ventura, Calif. Nevertheless, the scientists shipped the viable egg to a zoo for incubation.

Such egg losses aren’t surprising. Condor pairs often fail in their first attempt at parenting, Austin notes. However, to encourage the adults to continue their nesting behavior, he and his colleagues replaced the two eggs with a single wooden surrogate.

“We’ve already observed a female coming right back and sitting on that fake egg,” Brooks says. If these birds continue to exhibit good parenting habits, he says, “the plan is to replace the fake egg with a viable [zoo-bred] one that’s due to hatch on June 18.” The only question now, he says, is how close to the hatching date to execute a swap.

This is the first year that any condor released from the captive-rearing program would have reached reproductive age. As such, “these birds are right on schedule in terms of . . . attempting to start a family,” notes Mike Spear of the federal agency’s California/Nevada operations office in Sacramento, Calif.

Alas, successful reproduction offers no assurance that wild condors will thrive. Lead shot taints much of the carrion upon which they feed, and lead poisoning killed many of the wild-born condors originally in the area. Eight of the released birds died during just the past year. An autopsy on the last of these, which had just reached reproductive age, confirmed that it succumbed on Jan. 31 to lead poisoning.

Janet Raloff is the Editor, Digital of Science News Explores, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer, specializing in toxicology. To her never-ending surprise, her daughter became a toxicologist.