A new study by the Wildlife Conservation Society (WCS), Idaho State University, and the U.S. Geological Survey suggests that habitat fragmentation and the addition of makeshift perches such as transmission polls in sagebrush ecosystems are creating preferred habitat for common ravens that threaten sensitive native bird species, including greater sage grouse (image). The study appears in the January issue of the journal The Condor: Ornithological Applications. Authors include Dr. Kristy Howe of the Wildlife Conservation Society and Idaho State University, Dr. Peter Coates of the U.S. Geological Survey, and Dr. David Delehanty of Idaho State University. The authors looked at 82 raven nests on the U.S. Department of Energy's Idaho National Laboratory land in southeastern Idaho, a sagebrush steppe ecosystem where ravens increased in numbers eleven-fold between 1985 and 2009. The study area has been subject to various alterations such as the addition of transmission lines, roads, and other human construction. Results showed that 58 percent of raven nests were located on transmission poles, 19 percent were in trees, and 14 percent were on other human-made towers. A 31 percent decrease in the likelihood of nesting by ravens was observed for every one kilometer increase in distance away from a transmission line when compared to unaltered areas. The authors noted that the transmission poles are taller than any other object in the study area and that nesting in or near them may afford the raven myriad advantages including a wider range of vision, greater attack speed, and easier take-off. Nesting on the poles may also gain them greater security from predators, range fires, and heat stress.
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