The canyon smelled of campfire smoke when a team of biologists arrived at the Sespe River, a slow-moving, boulder-littered stream about 50 miles north of Los Angeles. The western side was blackened and covered in ash from the Thomas Fire, the largest fire ever recorded in California. Prickly pear cactuses drooped on the denuded hillsides, and oak trees still stood in a few spots that avoided the worst of the blaze.

The biologists from the U.S Fish and Wildlife Service’s Condor Recovery Program were on the trail of Condor 871, the eight-month-old California Condor chick that—until recently—lived there. Last month, the Thomas Fire burned over the chick's nest located in the canyon. In total, the blaze scorched 440 square miles, destroyed over 1,000 structures, evacuated 100,000 residents, and required 8,500 firefighters from December 4 until the fire's full containment January 12.

In the days leading up to the fire, a live video feed from the nest, which had a dedicated online following, showed 871 taking short practice flights, but she had never truly flown. Joseph Brandt, a wildlife biologist with the recovery program, said chicks typically leave the nest much earlier, but for some reason 871 seemed to be waiting until the last minute.

As the fire approached, the biologists confirmed that she was still alive by tuning into the radio signal emitted by a transmitter attached to her wing. But when the fire reached the nest, her signal vanished.

With a wingspan of nine-and-a-half feet, California Condors once soared over most of the western United States. But by 1982 the population dwindled to 23 birds largely due to lead poisoning caused by eating animal carcasses containing lead bullets. The U.S Fish and Wildlife Service captured the remaining condors in 1987, and five years later started releasing them back into the wild. By 2016 the wild population had grown to 276 condors.

Even though the fire was intense, Brandt felt optimistic that Condor 871 had survived. In 2010, he presented data at an ornithology conference showing that since the reintroduction of condors in Southern California, wildfires had burned six active nests, and five of those chicks survived.

“These wildfires are something that condors are adapted to,” he said. “For as long as there have been condors, there have probably been wildfires in this part of California.”

He had more recent evidence, too: Five days before the search, another member of the Condor Recovery Team had picked up 871’s signal while hiking along the canyon’s ridge. And in the days following the fire, a GPS unit on her mother’s wing sent back a series of pings from the east side of the river. Brandt suspected that’s where the chick was.

Lines of red fire retardant still stained the sides of the canyon as the group crossed the river on January 2, about two weeks after the fire burned through the area. Nadya Seal Faith, a research associate at the Santa Barbara Zoo who works closely with the recovery program, switched on her radio receiver and tuned to the frequency for 871’s transmitter. If the condor was nearby, she would have heard a consistent beep, but the speaker emitted only static. They kept walking, kicking up small clouds of ash with each step.