In 1982, the U.S. Fish and Wildlife Service made a controversial decision to capture the remaining 22 California condors in the wild as a lastditch effort to manage the species gene pool for recovery. With an intensive captive breeding program and gradual releases, 209 are now reestablished in the wild, and 182 remain in captive breeding programs. The numbers are promising, but a long road remains for recovery.
Rescuing the California condor from nearextinction has been a laborintensive effort and a case study in adaptive management. Hopper Mountain National Wildlife Refuge Complex, headquarters of the California Condor Recovery Program, continues to play a key role in that effort.
Interns and volunteers spend 10,000 hours annually at Hopper Mountain Refuge, studying, monitoring and occasionally rescuing the condors that nest and roost there.
While the refuges 2,471 acres of rugged canyons and mountains 60 miles northwest of Los Angeles are formidable for humans, condors can traverse them in minutes with their nineandahalffoot wingspan. Like many refuges that protect farranging birds, Hopper Mountain is just a small piece of condors required habitat.
The recovery program is an extensive network of partners, including zoos, nonprofit organizations and government agencies. Over decades, it has evolved and adapted with changes in technology, science and experience. For example, after newly released condors died from powerline collisions, mock power poles were placed in the pens of birds being prepared for release. The poles emit mild shocks, conditioning the condors to avoid perching on them, which helps prevent collisions after the birds are released.
Transmitter advances since the 1980s have helped scientists track condors ever more effectively than they did using bird counts. First came radio transmitters attached to birds to track individual condors in real time. Since 2004, GPS transmitters have complemented that technology by relaying location data and showing patterns of condor travel and congregation. VHF transmitters relay a particular signal pattern when a bird shows no movement for 12 hours, helping scientists rescue distressed birds or identify a cause of death.
Analyzing condor deaths helped scientists trace the leading cause of California condor mortality to lead in ammunition. Since the recovery program began, 36 percent of known freeflying condor deaths have been attributed to lead poisoning. Lead poisoning occurs when condors scavenge carcasses with lead bullet wounds, or eat leadlaced innards of a fielddressed animal. Since 2008, the states California Condor Preservation Act has required all hunting ammunition in condor territory to be certified nonlead, but other lead sources still may be problematic.
Further challenges lie ahead. For California condors to be downlisted from endangered to threatened status, there must be two distinct populations of 150 selfsufficient individuals in the wild, each with 15 breeding pairs. Now, there are 14 breeding pairs in California and five in Arizona. The selfsufficiency requirement may prove difficult because, to keep wildhatched chicks alive, staff or volunteers make monthly visits to cliff or treetop nests to remove bits of glass, metal and plastic that parents feed chicks. Scientists suspect condors misidentify such trash as calcium, like bits of bone. Chicks can eat and regurgitate small amounts, but if trash builds up in nests, it blocks the chicks digestive tracts. Cleaning greatly increases a chicks survivability.
As the condors population grows, the birds are expected to spread across a 5,000squaremile range. That has conservationists and wind industry officials worried that condors will collide with wind turbines in central California and elsewhere. Industry officials recently approached the refuge seeking to study solutions to prevent collisions. Were really at the infancy of this research, says refuge manager Michael Brady.
With more condors to track, the Service increasingly will rely on remote telemetry stations and GPS transmitters, says refuge biologist Joseph Brandt: We will manage them more as a population, less as individuals.
Kendall Slee is a Coloradobased freelance writer.