In winter, an iconic bird of America’s western plains and foothills benefits from fewer predators and a diet solely of high-protein sagebrush leaves.
By Rex Graham
The threatened Greater Sage-grouse snips and swallows fragments of leaves, unfazed by winter snow and freezing winds.
The tracks of the obligate sagebrush species are most common in the densest stands of the hardy shrub. The birds prefer Big Sage and tend to avoid the bitter tasting Mountain Big Sagebrush and Alkali Sagebrush. Those two and other sagebrush species produce monoterpene chemicals in their leaves that discourage herbivores.
Greater Sage-grouse vigilance
The sage-grouse is just as picky about where it walks, always vigilant for opportunistic predators. Wildlife biologists and other scientists who witnessed 266 grouse being killed said the most common predators were eagles, owls, coyotes and red foxes.
Nest cameras have revealed that Common Ravens, badgers and coyotes are frequent egg thieves. Some experts believe that eliminating ravens would help sage-grouse, but mathematical models suggest otherwise: “Removing Common Ravens can increase nest success, although not necessarily sage-grouse abundance,” Utah State University biologists reported in 2016 in the Journal of Wildlife Management.
Death by 1,000 cuts
Thousands of miles of overhead power lines, roads, wildfires, housing subdivisions, oil and gas infrastructure, wind-energy infrastructure, and invasive plant species are part of “a death by 1,000 cuts” to sage-grouse habitat, said Obama Administration Interior Secretary Sally Jewell. Sage-grouse numbers have fallen by roughly 90% since the 19th Century.
Today, keen-eyed avian predators sit-and-wait on power lines and poles for sage-grouse to appear. Eagles and hawks use this strategy to efficiently hunt large areas. Powerlines themselves are dangerous. A study reported in 2006 that power line collisions accounted for 33% of the deaths of sage-grouse less than 1 year old. Power companies argue that burying power-transmission lines is too expensive.
Sage-grouse of all ages and many other wildlife species die in collisions with fences. Vehicles also take a toll. Most carcasses are removed before researchers can even count them.
Peril from above – powerlines
A 2016 study by the National Wind Coordinating Collaborative reported that of hundreds of nests monitored, the nests that failed were all within 3 km of an overhead power line or 6 km of a road. Where human development intrudes into their wilderness, sage-grouse and other animals lose.
“Fragmentation” is the antiseptic term biologists use to describe the cumulative and devastating ecological impact of farming, wind-energy development and oil and gas production. The sage-grouse’s sagebrush habitat has fractured like a dropped dinner plate. The former habitat abundance for sage-grouse and other sagebrush species has disappeared like warm gravy through the broken pieces. Where possible, conservationists are working feverishly with land owners to rejoin and repair the dinner plate.
Even minor habitat fracking, such as ponds constructed by coal-bed natural gas developers, pose a threat. Mosquito larvae grow in the ponds, and the adults spread West Nile Virus to birds. Sage-grouse and members of the crow family are extremely susceptible to West Nile and can become “amplifying hosts” that can spread the virus.
The creeping expansion of conifer trees over decades also has consumed prime sagebrush habitat. In a positive sign, sage-grouse quickly returned to southeastern Oregon where the Sage Grouse Initiative removed conifer trees on “priority private lands” where sagebrush was replanted.
Removal of piñon and juniper trees and replanting sagebrush in Colorado had a similar positive effect on the endangered Gunnison Sage-grouse. That geographically isolated species is approaching extinction on dwindling, fragmented and degraded habitat.
Moderately fragmented sagebrush habitat may look natural and scenic to humans, but not to the animals that rely on it. For example female sage-grouse and Pronghorn Antelope avoid prime sagebrush that’s too close to trees or man-made objects. Unbroken, unfracked sagebrush habitat is crucial.
Not yet ‘endangered’
Pronghorns skittishly approach oil wells and wind-energy developments. They fear anything that predators can hide behind.
“We recommend efforts to conserve Pronghorn habitat such as constructing wells away from sagebrush, using existing roads to service newly constructed wells, and re-vegetating well pads with sagebrush plantings once they are no longer in use,” University of Alberta and North Dakota Game and Fish Department researchers said in the Journal of Wildlife Management.
In southeastern Wyoming, wind turbines didn’t scare 160 female Greater Sage-grouse from nesting nearby. The females were monitored with radio-tracking devices. However the hens gave a wide berth to infrastructure associated with the turbines, paved roads and, of course, overhead transmission lines.
Where politically feasible, progress has been made.
The U.S. Fish and Wildlife Service in 2015 said conservation efforts had “significantly reduced threats to the Greater Sage-grouse across 90% of the species’ [remnant] breeding habitat.” As a result, the service said the sage-grouse does not warrant protection under the U.S. Endangered Species Act.
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