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Greater sage-grouse are birds that occupy the semi-arid deserts of Eastern Oregon. Sage-grouse feathers are colored to hide the birds among the volcanic scab rock and sagebrush areas they occupy. Males have white showy breast feathers during the breeding season and are larger than females – six and a half pounds and three pounds respectively. Females retain camouflage feathers throughout the year.
As the name suggests, sage-grouse are sagebrush “obligates,” meaning they are dependent on sagebrush for reproductive success and year-round survival. Sage-grouse are also recognized as a landscape species with an annual range that can cover several hundred square miles. However, they are very selective in which areas are used seasonally within these vast landscapes, and often return to these same areas year after year.
Sage-grouse seek areas of dense sagebrush canopy cover and healthy understory of native grasses and forbs to conceal their nests from predators. The location of nesting females attracts males to congregate on leks (breeding grounds) to conduct their breeding displays. After chicks are hatched – typically in late April or early May – they learn to forage near the nest site. As broods mature, females will lead their young to moist areas often higher in elevation or they may use natural meadows and irrigated hay or alfalfa fields. Chicks are largely independent from the brood female by September or October.
As the desert dries out in fall, sage-grouse shift their foraging to a diet of sagebrush, which will comprise nearly all of what they eat until the following spring. Amazingly, during this period young birds continue to grow to nearly adult size, and adults gain 10 to 15 percent of their body mass eating nothing but sagebrush. The availability of sagebrush above the snowpack is critical to winter survival of sage-grouse. Winter habitat can vary from low sagebrush exposed on wind swept ridges to tall dense stands of basin big sagebrush in valley bottoms.
Oregon is home to approximately 6 percent of the world’s sage-grouse population, and is a relative stronghold for the species, however even in Oregon sage-grouse populations have declined . Sage-grouse are found in Union, Baker, Deschutes, Crook, Lake, Harney, and Malheur Counties. Approximately 70 percent of sage-grouse habitat in Oregon is managed by the BLM, 21 percent is privately owned, and 8 percent is under state or U.S. Forest Service Management. Across this wide landscape and varied ownership, sage-grouse face multiple threats.
The three primary threats to sage-grouse in Oregon are encroaching juniper trees, invasive annual grasses, and wildfire:
- Encroaching juniper woodlands eventually crowd out the grasses, forbs and sagebrush that sage-grouse need to survive. They also provide perches and cover for sage-grouse predators, and because of this, sage-grouse avoid juniper trees even at very low cover levels.
- Invasive annual grasses, such as cheat grass and medusa-head rye invade low elevation and degraded sagebrush sites, these species can outcompete native forbs, and provide a continuous fuel bed that spreads wildfire. Following wildfire, these grasses quickly sprout from seed and can completely convert habitat from native sagebrush communities to annual grassland with no value to sage-grouse.
- Wildfire kills almost all affected sagebrush shrubs, and due to the ecology of sagebrush, it may take 20 to more than 150 years before sagebrush cover returns to pre-fire levels. Very large fires (>100,000 acres) fueled by cheatgrass, are increasing in frequency, and may burn over the entire range of some sage-grouse populations, reducing available sagebrush cover by more than 75%. Sage-grouse quickly return to burned leks and nesting areas following fire, and try to persist in this fire altered habitat, which leads to greatly reduced survival and nest success, and may eventually lead to the extirpation of populations.
Other threats to sage-grouse in Oregon include human development, feral horses and burros, West Nile virus, and increasing common raven populations among others.
Sage-grouse are vulnerable to changes in their habitat because they are relatively long-lived (three to seven years) compared to other upland game birds (one to two years). They also lay seven to nine eggs compared to 12 to 14 eggs laid by other upland game birds. The result is a species that is quick to decline after disturbance yet slow to recover because of lower productivity.
Sage-grouse exhibit strong fidelity to nesting and lek areas and winter range, returning to the same areas each year. If a large disturbance occurs and removes these habitats, often the birds continue to try and survive in these areas, typically to their detriment.
Multiple organizations are involved in efforts to address these threats and conserve sage-grouse in Oregon, more information can be found on our sage-grouse conservation sub-page (link). Maps of sage-grouse habitat and threats can be accessed online at the SageCon Landscape Planning Tool.
ODFW allows a conservative hunting season in some areas of the sage-grouse range in Oregon. The carefully managed hunts have harvest levels well below the level believed to impact populations. ODFW’s self-imposed policy is not to harvest more than five percent of projected fall sage-grouse populations and in practice, the harvest is about 2.5 percent. Scientific research has found these harvest levels did not affect the size of the subsequent breeding population.
Hunters are asked to submit one wing to ODFW from each bird harvested. The wings allow ODFW to calculate age ratios, sex ratios, peak hatch dates and proportion of successful hens. In the past, hunters have even submitted blood samples from harvested birds for other research on West Nile virus. ODFW will likely maintain some limited harvest, which will provide a limited recreational opportunity while at the same time allowing the collection of biological data that would be difficult and/or expensive to collect in other ways. |
