Cattle Increase Occurrence of Ravens That Prey on Sage Grouse
02 / 03 / 2016, USGC
Summary: DIXON, Calif. – Ravens are almost fifty percent more likely to inhabit areas in sagebrush landscapes if cattle are present, and preferentially select sites near greater sage-grouse breeding grounds.
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DIXON, Calif. – Ravens are almost fifty percent more likely to inhabit areas in sagebrush landscapes if cattle are present, and preferentially select sites near greater sage-grouse breeding grounds.
These findings have implications for greater sage-grouse management practices aimed at reducing raven predation on sage-grouse nests, according to research published in Ecosphere.
Raven abundance in the sagebrush-steppe of the American West has increased three-fold during the last four decades, mostly as a result of unintended food and water subsidies from human land-use practices. Predation is the primary source of sage-grouse nest failure, and reducing ravens access to food and water subsidies could assist with conservation efforts. While removal of ravens may reduce their local abundance in the short term, removing subsidies that promote ravens will likely be more effective for long-term control of raven predation.
U.S. Geological Survey and Idaho State University scientists examined the influence of livestock on common ravens in about 400 square miles of sagebrush-steppe ecosystem in southeastern Idaho. Grazing by livestock in these systems is common practice on many public lands, but potential influences of livestock on ravens are poorly understood.
“Common ravens are a known predator of numerous species including the greater sage-grouse,” said lead author and USGS scientist Peter Coates. “This study provides information to help rangeland resource managers develop conservation actions that focus on increasing the reproductive success of greater sage-grouse. For example, limiting raven access to livestock resources, such as water troughs, and adjusting the timing of livestock access to sage-grouse breeding areas during the spring, would likely reduce raven predation on sage-grouse eggs.”
Research findings include:
The probability of raven occurrence increased by 45.8 percent in areas where cattle were present.
Ravens preferentially selected areas near sage-grouse breeding grounds, called leks, especially at sites where cattle were present.
Landscape characteristics also influenced raven occurrence. For example, ravens selected relatively open (fewer trees) low elevation areas, specifically those with cropland, wet meadow and urbanization.
The study was a partnership of the USGS, Idaho State University, and Idaho Department of Fish and Game. The journal article is available here. Additional project information can be found at the USGS Western Ecological Research Center website.
About Greater Sage-Grouse and the Great Basin
The Great Basin comprises more than 72.7 million hectares (more than 179 million acres) across five states: Nevada, Utah, Idaho, Oregon and California. Wildfire has been identified as a primary disturbance in the Great Basin.
Greater sage-grouse occur in parts of 11 U.S. states and 2 Canadian provinces in western North America. Implementation of effective management actions for the benefit of sage-grouse continues to be a focus of Department of the Interior agencies following the decision by the U.S. Fish and Wildlife Service that the species is not warranted for listing under the Endangered Species Act.