"Dirt" Is Part Of Sage Grouse Diet

PINEDALE –Sage grouse are arguably best known for their courtship displays on the “lek” in April. But many west-central Wyoming sage grouse are gaining a little winter notoriety: frequenting the “lick.”

While the lek is the courtship grounds, the lick is the eating grounds – literally. This trademark game bird of the West has been documented eating soil in the winter from the Big Sandy drainage south of Boulder, west to Big Piney and north to Daniel, plus a few Jackson Hole locations.

Soil eating is scientifically known as geophagy and had been documented in many species, with parrots probably leading the overall list with their taste for clay. A spattering of other birds, ungulates and even some humans in various cultures across the globe are known for ingesting soil in some circumstances.

In the last 15 months, Dale Woolwine and Bureau of Land Management cohorts have discovered at least 15 of these sage grouse soil-eating grounds in the Upper Green River Basin.

On Jan. 23, 2013, Woolwine was afield south of Boulder checking a fence with a history of sage grouse collisions. He flushed a concentrated flock of birds and found a living-room-sized area with so much sage grouse activity the snow was completely packed down or melted. There were golf ball sized divots in the ground the birds had pecked. Trails led to the site from various directions.

The same day, Woolwine, who knows sage grouse well from his 10 years of working with the species, found another similar site and knew he was on to something. “Soil eating by sage grouse was outside of the literature and anything mentioned by the experienced sage grouse biologists I trained with,” Woolwine said. “I recognized it was something that probably hadn’t been noticed before – and certainly important.”

The two licks had something in common: low-lying areas with alkali residue. He started visiting similar locations and in the last two winters, he’s documented 15 sage grouse geophagy sites -- and six are on or within a couple hundred yards of known leks.

Woolwine shared the discoveries with associates and found out dirt diners had also been documented in Jackson Hole. In March 2007, Bryan Bedrosian, discovered sage grouse eating from gravel piles in Grand Teton National Park. That spring, the wildlife biologist and associates from Craighead Beringia South, also detected that the first lek to attract sage grouse in Jackson Hole each breeding season also sports an eroded cutbank attracting pecking sage grouse. This spot on the National Elk Refuge is well-known as a natural mineral lick for elk, bison and pronghorn.

And soil eating is not being mistaken for picking up grit. Sage grouse don’t have a grit-enabled muscular gizzard, because they’re engineered to eat only soft food: leaves, insects and at least in west-central Wyoming, fine soil.

Why in the more than 200 years of settlement of the West and 60 years of serious sage grouse study has the behavior just come to light in the last seven?

“The bird just rarely had any eyes focused on it from the close of hunting season to breeding season,” said Tom Christiansen, sage grouse coordinator for the Game and Fish Department. “Most sage grouse habitat is difficult to access in winter with too much snow for trucks and too little for snow machines. Aerial surveillance is unable to detect that small of detail.”

Soil eating appears to be very gregarious; from a half dozen birds to more than 80 have been on a lick together. Soil also appears to be almost exclusively a breakfast food with very few birds seen at the dirt diners after 10 a.m.

“These geophagy sites are making us rethink that there’s more to winter sage grouse habitat than just exposed sagebrush above the snow,” Woolwine said.

Why sage grouse are eating soil is yet only speculation. The first reaction was “hens are after calcium” for egg laying. But both hens and roosters are eating soil. Is the species lacking a mineral they get from another source in the summer? After switching to a nearly exclusive sagebrush diet in late fall, could sage grouse be in need of something to help buffer or metabolize the resins in sagebrush? Woolwine and Bedrosian, in conjunction with Wyoming Wildlife Consultants, are applying for research grants to help get some answers.

Trail cams have figured out a couple of the licks in the Big Sandy drainage are dual sage grouse/pronghorn sites. The pronghorn usually get their soil fix later in the day, but the two species have been on site together several times.

Noted Wyoming wildlife biologist and hunter, Harry Harju, has witnessed not only pronghorn, but also elk and deer geophagy. In the Shirley Basin north of Medicine Bow, Harju’s seen pronghorn and elk eating soil from alkali depressions as recent as October 2012. Along Horse Creek south of Jackson, both elk and mule deer were observed taking bites from an exposed sidehill in the ‘70s.

Research in the ‘80s documented grizzly bears dirt dining in Yellowstone National Park, particularly when emerging from hibernation.

Christiansen suspects other sage grouse geophagy sites are just waiting to be documented across Wyoming and possibly the West. Anyone visiting sagebrush areas in the winter is asked to keep an eye out for disturbed, low-lying, alkali areas, particularly with greasewood. If you suspect they’ve found a lick, please contact Christiansen at: tom.christiansen@wyo.gov.
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Location : Central WyomingWyoming
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