Predator Control Considered for San Miguel Basin

SAN MIGUEL COUNTY – Gunnison Sage-grouse populations living in the San Miguel Basin appear to be losing ground in their battle for survival and predation is looking more and more likely as a main culprit in their demise.

Colorado Division of Wildlife researchers counted 25 males on 11 known breeding areas throughout the area, called leks, during their annual spring count of the birds.

The numbers represented the fifth straight year of local population declines as of 2006. That year researchers counted 77 males followed by 66, 44 and 33 in 2007, 2008 and 2009, respectively. Counts of females are less reliable because they are so well camouflaged.

A total of 123 Gunnison Sage-grouse are now estimated to remain in the San Miguel Basin.

“The one place where we’re sure we have a good idea of what’s happening is the population around Miramonte,” said Leigh Robertson, coordinator of the San Miguel Basin Gunnison Sage-grouse Working Group, referring to the Miramonte Reservoir area that is home to the San Miguel Basin’s core population.

This year researchers counted 14 males there, down from 18 in 2009.

“We know that predation is an issue there,” she said.

While the native range of the Gunnison Sage-grouse once spread throughout New Mexico, northeastern Arizona, Colorado, and Utah, today only 10 percent of that range is estimated to remain in seven populations totaling about 4,000 breeding individuals located in isolated areas of southwest Colorado and southeast Utah.

The core population is located in Colorado’s Gunnison Basin where it numbers about 3,000. Other Colorado populations are located on Pinion Mesa and in Crawford, Dove Creek, and Poncha Pass, and near Monticello, Utah.

Last fall the CDOW fitted 30 birds from the Gunnison Basin with radio collars and transplanted them into the Dry Creek Basin area.

“They did well in the late fall and early winter,” said Montrose-based CDOW Wildlife Conservation Biologist Jim Garner. “But this spring we lost a lot of birds.”

Eleven of the transplants were killed. Bbecause avian predators tend to pluck whole feathers from their prey, the presence of broken, crunched up feathers suggested mammals were largely to blame for the losses.

“Just about everything eats these things,” said Garner, reciting a list of predators including coyotes, foxes, badgers and bobcats.

“But we’re seeing a lot of coyotes,” he continued.

Parts of radio collars have also been recovered from coyote scat in another telltale sign.

In recent years chick survival in the San Miguel Basin has also been poor.

“The chicks that are hatching are only lasting a week or 10 days before something is getting them,” said Garner.

Last year Fort Collins-based CDOW Wildlife Researcher Mike Phillips placed radio collars on a total of eight adult birds in the Miramonte area, four of them nesting females, as part of a demographic study. Each of the four hens lost her brood for a total loss of 12 chicks.

This year proved no better around Miramonte.

“No chicks hatched this year,” he said.

“We’re not seeing any recruitment out here and haven’t seen it for several years.”

Because Gunnison Sage-grouse females will generally adopt chicks that are not their offspring, there is hope for a captive rearing project for which Phillips is the co-principal investigator.

Now in its second year, the investigators are trying to determine when best to reintroduce the chicks back into the wild with a hen and her brood for maximum adoptability and survival.

“If they’re less than one week old the adoption rate is really high,” whereas older chicks may not be adopted as readily, Phillips said.

That said, the younger the chick the higher the risk it will die, so holding onto chicks until they are older could mean more live long enough to eventually reproduce.

Regardless, predation of the core Miramonte population has become such a problem that that Phillips has been neither willing nor able to release the chicks there, instead placing them with broods in the Gunnison Basin.

So far initial survival rates of 30-40 percent are a little higher than would normally occur in the wild, but it’s still too early to say whether the project will ultimately be successful.

“We will know better this winter,” he said, adding that in a year’s time he’ll know the annual survival rate.

Although predation is natural and healthy populations can sustain some loss, local Gunnison Sage-grouse numbers have fallen to such low levels that the survival of every remaining bird has become critical.

“Another drought event or hard winter could wipe these birds out,” Garner said.

With local numbers hovering around 25 percent of healthy population targets despite a decade-long quest to improve their habitat and the more recent transplant efforts, local DOW staff is strongly considering writing a predator control plan to try to save them.

While still being “intensely debated” by agency staff, according to CDOW Terrestrial Biologist Brad Banulis, it could include gunning coyotes, fox or bobcats in very specific target areas as early as this winter. Avian predators could also be considered.

“We’re not sure if this is where we want to go,” said Banulis, indicating that the agency will seek more public input before any such action is take. Nevertheless, the agency is contemplating the politically and socially unappealing option because, “It’s a dire situation for the [Gunnison] Sage-grouse in the San Miguel population,” he continued. “This is a last resort option.”

The situation has, in fact, become so desperate for the birds that the local working group supports the idea, Robertson said.

“What we’ve been doing alone hasn’t worked,” she said.

“We just don’t want to lose the birds and we think it might be what’s necessary, at least in the short term, to keep that population from dying out.”

Robertson said that recent research indicates that predator control can be helpful when trying to transplant animals.

“That’s why we’re willing to look at that,” she said.

“In an ideal world we wouldn’t prefer it,” but at this point, “Most of the people don’t feel like we have an option.”