Common ravens are intelligent omnivores that regularly consume the eggs and young of nesting birds, and their populations are boosted by human-provided food and nesting resources. This has resulted in elevated predation by ravens on many sensitive prey species, including greater sage-grouse. A study in The Journal of Wildlife Management indicates that coating developing raven eggs with non-toxic mineral oil helps to protect sensitive prey populations by reducing raven reproduction.
Investigators found that egg-oiling—a management technique which stops the developing raven embryo from surviving without destroying the egg itself—reduces local raven numbers and improves nest survival and population growth of greater sage-grouse, one of the vulnerable prey species targeted by ravens.
"Applying egg oil to raven nests offers nesting sage-grouse some reprieve from nest predation. When raven nests were treated, sage-grouse nest survival more than doubled and relative abundances of sage-grouse increased by 44% compared with control populations," said leading author Steven Mathews-Sanchez, PhD, who conducted this work while at the US Geological Survey Western Ecological Research Center and who is currently a biologist for the San Diego Zoo Wildlife Alliance. "Although highly effective at a local scale, egg oiling does not address the anthropogenic sources driving raven population growth, which must ultimately be addressed to protect sage-grouse and other sensitive species, nor does it address critical habitat required for sage-grouse to persist long-term."
URL upon publication: https://onlinelibrary.wiley.com/doi/10.1002/jwmg.70247
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