Soaring high overhead, circling upwards on thermals that lift wings spanning nearly 10 feet from tip to tip, California condors are one of the world's rarest birds. And while humans have helped immensely to recover their populations, humans also are standing in the way of recovery.

Twenty years into an ambitious recovery plan, though the birds are expanding their territory in the Southwest, their recovery is tenuous. Life as a condor in the region, you see, is not an easy one because of deadly risks they encounter, from lead shot in gut piles left behind by hunters to electrical wires that can deliver a deadly shock to them. And then there are somewhat even more unusual threats.

"We've had a lot of trouble in particular off Plateau Point, which is a popular area where people like to throw coins to make wishes," said Grand Canyon wildlife biologist Miranda Terwilliger. "That's unfortunate, because the birds eat them and it congests in their gut and can kill them. We also had a lot of troubles early on with birds sitting on electrical wires. Because they're so big, they tend to make a conduit (and electricute themselves). We've managed to successfully retrain a lot of the newer birds on that by having a fake electric pole that's very slightly with a shock in it. Enough to make them realize this is not the kind of thing I want to sit on."

While nearly 200 condors have been released in the region since the recovery program got under way, there were just 79 birds counted by the U.S. Fish and Wildlife Service during its most recent review of the program. Just nine of those condors were hatched in the wild, with the rest coming from captive breeding operations.

The biggest impediment to the recovery operation, the agency noted, is lead shot.

Although targeted voluntary efforts to reduce the use of lead ammunition in California condor range has reduced the amount of available lead seasonally, further efforts to reduce the greater lead load available to scavenging birds on a year-round cycle are crucial for program success and a healthier ecosystem.

While the Obama administration banned lead shot and lead fishing tackle, Interior Secretary Ryan Zinke overturned that ban last March on his first day in office, saying that the ban "was issued without significant communication, consultation or coordination with affected stakeholders."

And yet, lead shot is viewed by federal agencies as the No. 1 killer of condors in the wild.

"The majority of our loss we've been able to attribute to lead poisoning," said Ms. Terwilliger. 

According to the Fish and Wildlife Service, however, lead poisoning was responsible for the deaths of 37 condors since the recovery program began in 1996. Eighteen of those deaths were recorded between 2012 and 2016, the agency noted in its review. The fatalities due to lead could be higher, though, as three deaths over the past 20 years were suspected to be related to lead poisoning, 39 birds went missing, the deaths of 16 were undetermined.

"Lead comes into play primarily on private and Forest Service land, BLM land, the Vermilion Cliffs, the Kaibab National Forest where hunters are using lead ammunition. And they shoot animals, and because of the way the lead disperses in a carcass, usually there is some left in the gut pile," said Ms. Terwilliger. "Hunters typically leave the gut piles. We've known particularly with the birds, they do follow the gut piles.

"For example, when the deer hunt for the Kaibab Plateau opens on the Forest Service land, a lot of birds hang out there because there's more food available for them. And condors are actually less susceptible to lead poisoning than, say a bald eagle, but they're more likely to get it, because they are obligate scavengers, whereas a bald eagle doesn't have to (scavenge). So they get exposed more," she added. "We think most of it is from lead ammunition that is still in the environment, either in recent gut piles or it's in the environment for some other reason, older lead. It's really hard to know exactly where they're getting the lead poisoning."

Those working on the condor recovery have had some success in getting hunters to understand why lead shot is so detrimental to condors by showing them how readily the shot disperses in an animal's body vs. other non-lead shot and through education programs. As a result, more and more have switched to non-lead shot. But the problem is huge.

Eighty to ninety percent of big-game hunters in much of the Arizona portion of condor range have participated in the voluntary program since 2007, and the percentage of hunters participating in (Utah's) program reached this level in 2016. Models have suggested that simultaneously successful voluntary lead reduction efforts in Arizona and Utah could result in a level of condor fatalities due to lead toxicity that would allow the population to increase (Green et al. 2008). However, modeling based on the population in California predicted that even if only 0.5% of carcasses are contaminated with lead, the probability that a condor would feed on a contaminated carcass over a 10-year period is 85-98%.-- U.S. Fish and Wildlife Service

While this trio of condors was spotted over Grand Canyon, more of the birds are turning up at Zion National Park to the north in Utah/NPS

In spite of the lead shot problem, condors have been dispersing north from Grand Canyon, with the big birds having been spotted at Bryce Canyon National Park, Cedar Breaks National Monument, Glen Canyon National Recreation Area, and Zion National Park, all in Utah, with some birds nesting in Zion.

"So far they have not had a successful nest," said Ms. Terwilliger, referring to the Zion condors, "however, birds definitely are spending more and more time up there. In fact, this winter we had very few birds hanging around here. Most of them went up to the Kolob region of Zion National Park.

"Primarily right now they spend their time at Grand Canyon or Zion, and Zion is really stepping up doing some of the same monitoring that we're doing here at Grand Canyon. We share all of our data, so we can keep track of what's going on that way. But right now, there are more birds up there than we have down here at Grand Canyon at the moment."

While many human visitors to Zion National Park like to hike up to Angels Landing to admire the view of Zion Canyon, the birds seem to like that high spot as well.

"They've (park staff) actually had to haze some birds off Angels Landing," Ms. Terwilliger said. "We've had visitors sending us pictures of groups of seven condors up there last summer. There's definitely more activity going on. And at Grand Canyon we didn't have to haze any birds this year, which is awesome."

One reason the biologist believes the condors have been heading up to Zion National Park is the fact that disease among the park's bighorn sheep herds has led to a die-off, and there's more hunting in the areas surrounding Zion than around Grand Canyon.

While there are only about 80 condors in the wild in the Arizona-Utah area, Ms. Terwilliger noted that "we have the highest number of breeding birds in the wild than we've ever had. For a long time we had birds that were just too young to breed."

Then, too, once they breed, they typically only have one young a year, and then wait another two or three years before breeding again, she said.

At the end of the day, though, until lead shot can be removed from the environment, condor recovery will be affected, the Fish and Wildlife Service report concluded.

The condor recovery program in the Southwest has now been underway for 20 years, and the program continues to make progress in several key areas. Through intensive management and replacement of missing or dead condors with captive-raised birds, the overall number of free-ranging condors has remained near eighty individuals, and the birds are consistently using larger seasonal ranges. The number of breeding pairs has increased through this reporting period, and these pairs have successfully hatched and fledged chicks each year. Pre-release conditioning of birds seems to be helping to reduce or avoid undesirable behaviors. However, the most significant issue raised in the third program review, exposure to lead contamination, continues to be the chief impediment to recovery.