Wildfires are an unexpected threat to California condors

The California condor should never have been named the “California” condor. The largest bird in North America could once be found scavenging across much of the continent. But the birds’ numbers began to drop precipitously in the 1800s, and by 1937, the species had disappeared from everywhere except California. The decline continued, and only 22 birds remained in 1981. The next year, scientists took what eggs they could find and began a captive rearing program. The condor was declared “extinct in the wild” in 1987 when the last six wild birds were taken into the program.

Scientists began reintroducing the birds in 1992, and there are now more than 400 flying over California, Arizona, Utah and Baja California, Mexico. But the birds aren’t out of danger, a new study finds, and there may be a previously unrecognized threat to worry about — forest fires.

In the 1980s, as the condors were nearing extinction, there were several theories as to what was killing them — including human disturbance, food scarcity and eggshell thinning caused by DDT contamination — but the big killer is now thought to be lead poisoning. Condors are scavengers, and when they consume carcasses killed with lead ammunition, they get poisoned.

Because the condor population is so heavily managed now, scientists can track what happens to many of the birds flying in the wild. Terra Kelly of the University of California, Davis and colleagues tracked the fates of 220 condors (191 released birds and 29 born in the wild) from 1992 to 2011. Lead poisoning remains the biggest threat to the condors, the researchers report in the November Biological Conservation. But lead ammunition wasn’t the only killer.

Early on in the release program, many birds were killed when they came into contact with electrical wires or utility poles and were electrocuted. So in 1995, program managers began training birds to avoid these dangerous sites. Since then, few trained birds have died from electrocution.

The third biggest killer was the surprising one — wildfires. The scientists can’t say for certain that the forest fires killed any condors, but over the years, seven birds disappeared when wildfires burned through the areas in which they were living. While birds can generally fly out of the way of fire activity, condors may be at risk if a fast-moving wildfire burns through a place where the birds roost and nest at night, the researchers propose. If the fire is fast enough, the birds won’t be able to escape.

With a lot of help from humans, enough of the birds are living long enough that the population is beginning to stabilize, the team found. And efforts in California to start phasing out lead ammunition show real promise. But with California wildfires increasing in number and duration, they could threaten the California condor population. The birds gather in small flocks that roost together. A single fire could wipe out a substantial fraction of the species.

So even if the birds manage to survive our lead pollution — which is not guaranteed, because a flock of birds can be poisoned by sharing one big meal — the species is still in a precarious spot.