Field Notes
U.S. Fish & Wildlife Service
Field Notes Entry   
NEVADA FWO: Understanding Greater Sage-Grouse Threats in Nevada
California-Nevada Offices , February 6, 2012
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Pinyon and juniper encroachment into greater sage-grouse habitat.
Pinyon and juniper encroachment into greater sage-grouse habitat. - Photo Credit: USFWS

By Jeannie Stafford, Public Affairs, Nevada FWO

Habitat loss and fragmentation are the primary causes of greater sage-grouse population declines. They result from natural processes which may include, wildfires, invasion by non-native plants, or pinyon and juniper forest expansion or man-made activities such as energy development, construction of powerlines, roads, fences, and other physical infrastructure.

Greater sage-grouse cannot survive in areas where sagebrush does not exist. Sagebrush not only provides cover for greater sage-grouse, it constitutes 99 percent of their winter diet.

Wildfire and Invasive Plant Species
The interaction between wildfire and invasive plant species represents the single largest threat to greater sage-grouse in Nevada. Over the past decade more than three million acres of sagebrush habitat in Nevada has been impacted by wildfire, representing a loss of nearly 15 percent of available greater sage-grouse habitat. Burned area rehabilitation requires many years and can be further complicated by invasive nonnative species such as cheatgrass. Unfortunately, rehabilitation efforts continue to be surpassed by the wildfire frequency and expanse in Nevada.

Pinyon and Juniper Encroachment
Pinyon and juniper forests have been encroaching into key greater sage-grouse habitat at a rapid rate. Forest expansion removes available sagebrush habitat and creates barriers, fragmenting important greater sage-grouse habitats. In addition, these trees provide artificial roosting and nesting sites for greater sage-grouse predators.

Conversion of sagebrush habitats to industrial uses or any non sagebrush ecosystem condition removes these areas from greater sage-grouse use. Placement of energy and mineral developments in otherwise intact sagebrush communities can hinder movement of greater sage-grouse, ultimately leading to isolation of populations from each other or from important habitats.

Powerlines, roads, fences and other features that support human developments can alter the quality and use of sagebrush habitats by the species. These structures can lead to direct mortality. In addition, they facilitate the occurrence of predators and invasive species and act to fragment intact sagebrush habitats by creating both physical and behavioral barriers to greater sage-grouse movements.

Lek and Nesting Habitat Disturbance
Greater sage-grouse courtship begins on traditional strutting grounds (leks), where birds congregate to display and breed. Leks are typically used for many generations and represent the focal point for reproduction. However, successful reproduction depends on maintenance of surrounding nesting habitat. Degradation of these sagebrush sites can lead to reproductive failure of populations.

Meadow Degradation
Upland meadows and riparian habitats provide vital food sources for greater sage-grouse chicks and adults during the spring and summer. Degradation and loss of these limited habitats can have a significant influence on overall population health.

Grazing by native wildlife, feral horses, and livestock can influence the quality of sagebrush and meadow habitats. Changes to soil properties, loss of understory grasses and forbs, and degradation of sagebrush plants can present significant challenges to nesting success and chick recruitment in greater sage-grouse populations.

Greater sage-grouse are eaten by a variety of predator species. Species, such as common ravens, have increased dramatically in the Great Basin due to human activity. Their increased presence on the landscape can significantly alter the ability of greater sage-grouse hens to successfully raise young. Degradation of nesting habitat can greatly compound the degree of impact ravens and other predators exert.

Contact Info: Jeannie Stafford, 775-861-6300, jeannie_stafford@fws.gov
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