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Hunters have long provided wildlife scavengers with free meals. Those free lunches, however, sometimes come at a high cost.

An increasing willingness by Utah big game hunters to change their ammunition or remove animal remains to prevent lead poisoning of endangered California condors may be paying off.

The Peregrine Fund recently announced that its annual testing of blood from condors living in northern Arizona and southern Utah showed the lowest lead levels in a decade.

"The ups and downs of lead poisoning over the years demonstrate that any single season does not make a trend, but our test results are encouraging," Eddie Feltes, field manager for The Peregrine Fund's condor project, said in a release. "If this ends up being the beginning of a trend, we hope it will continue."

Only 16 percent of the condors trapped and tested by researchers starting in September 2013 showed extreme exposure to lead in their blood. That's a big change from the 42 percent of condors that showed extreme exposure in 2012.

Biologists treated 11 condors this past winter with lead-reducing chelation therapy. Last winter 28 condors had the same treatment.

Last fall Utah Division of Wildlife Resources officials added new incentives to reward hunters in the Zion unit, an area frequented by the rare birds. It runs from Interstate 15 on the west to Highway 89 on the east, State Road 14 on the north and to the Arizona state line on the south.

Hunters who showed up at area checkpoints with non-lead ammunition, or those who hauled out the entrails of animals they killed with lead ammunition, were entered in a drawing for an all-terrain vehicle or a new rifle.

Keith Day, the sensitive-species biologist with the DWR's southern region out of Cedar City, reported that 78 percent of the hunters contacted by DWR in October 2013 on the Zion unit were using non-lead ammunition. Eighteen gut piles were turned into the state for proper disposal, and 36 percent of successful hunters who used lead ammo reported that they removed the innards from the field.

"Participation was way up," said DWR wildlife section chief Bill Bates. "The biggest problem we had was the availability of non-lead ammunition. We have a proposal to run the program again this year. It will be dependent on funding."

Utah first provided incentives for using non-lead ammo in 2011, but less than 10 percent of the hunters took part. Roughly half the hunters on the Zion unit in 2012 participated, a year when the area was a draw-only unit and it was easier for the state to provide information.

"The half life of lead in blood is a very short period. That gives us a relatively good indication of where and when exposure may have happened," said Chris Parish, condor program coordinator for The Peregrine Fund. "The lower levels this year could absolutely be attributed to efforts in southern Utah and northern Arizona to reduce the amount of lead in ammunition. If this happens to be the first year in a series of declines that would be fantastic."

Twitter: @BrettPrettyman —

About California condors

The California condor is one of the largest birds in North America. From wing tip to wing tip, it measures 9.5 feet.

In 1982, 22 California condors were left in the world. With the help of biologists, they now number around 400, with more than half flying free in the wild.

Condors in the Southwest are deemed a nonessential experimental population through the Endangered Species Act.

As one of the longest-living raptors in the world, condors may live to be 50 years old or more.

Lead poisoning is the main threat to the survival of California condors.

See a video of condors from the Utah Division of Wildlife Resources here.