Rescued from the brink of extinction in the 1980s, the California condor is again soaring freely in the West due to a captive-breeding campaign enlisting all of the species' surviving adults.
But a new study warns that unsafe food sources and the captive condors' tame offspring could doom efforts to save the giant birds.
A third of the young condors released to date - 35 of 104 birds - have died, a fact the study's authors conclude is too high a cost for a species that numbers only 169 animals.
''The solution is an unpalatable one - and that's to bring these birds in for the good of the species,'' said the study's lead author, Vicky J. Meretsky, an assistant professor of conservation biology at Indiana University.
Biologists who work on the release program were critical of Meretsky's research, which appears in the August issue of the journal Conservation Biology. They said she and her four co-authors never spoke to them about their concerns.
They also believe it would be foolish to remove the captive-bred condors from the wild just as the oldest birds are nearing sexual maturity. They're eager to see if those condors will breed.
But Meretsky and her colleagues see two daunting problems facing the condor rescue effort: the overly tame birds yielded by the captive-breeding program, and the lead-poisoning deaths of condors that feast on animal carcasses riddled with lead buckshot.
This year alone, five birds have died from lead-poisoning and several others were captured and treated for ingesting the toxic metal.
Lead-poisoning nearly wiped out the California condor, a homely faced scavenger whose 9-foot wingspan make them North America's largest bird. By the time all the wild condors were rounded up in the 1980s for the breeding program, just 27 remained.
Wildlife biologists have succeeded in sparking condor reproduction by removing eggs from the captive females' nest-boxes so they will lay other eggs. The pilfered eggs are hatched in incubators, and the chicks reared by humans wearing hand-puppets resembling adult condors.
This technique has resulted in far more puppet-reared birds than those raised by their doting parents.
Despite efforts to reduce their exposure to humans, Meretsky said many of the puppet-reared condors approach humans to beg for food or to invade campsites. One bird even tore its way into a tent.
The puppet-raised birds' bad ways have also rubbed off on some of the parent-raised birds, Meretsky said. She fears a public backlash to the condor program if one of the sharp-beaked birds attack someone.
''It won't help the condors if something tragic happens,'' she said.
Since 1992, numerous groups of puppet- and parent-raised birds have been released at sites in California and Arizona.
Meretsky wants most the 46 condors in the wild reunited with the 123 captive birds due to persistent behavior problems. Many problematic birds have already been pulled from the wild, she noted.
The release program, which together with the breeding effort costs more than $1 million annually in federal, state and private funds, could resume next year using only parent-raised condors, she said.
While the puppet-reared birds have exhibited unnatural behavior, the problem just isn't that serious, said Lloyd Kiff, science director of The Peregrine Fund, a nonprofit conservation group in Boise, Idaho.
Kiff, who directs the group's condor breeding center, also said there's no conclusive evidence puppet-reared condors fare worse in the wild than their parent-reared cohorts. After all, both groups of birds are equally susceptible to lead-poisoning.
He thinks the program can overcome the birds' problems and still meet its goal of a self-sustaining population of 300 wild birds.
''I'm prepared to place a bet on it,'' he said.
Behavioral problems also arose when South American nations began trying to re-establish the Andean condor, said Greg Austin, a wildlife biologist with the U.S. Fish and Wildlife Service in Ventura, Calif.
But the young Andean condors wised up when they matured and their hormones kicked in, he said.
''Once those birds starting breeding, their misbehavior stopped and they started acting like wild condors,'' Austin said. ''We believe the same thing will happen with our condors.''
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